I'm so sorry for your loss. I know it's very painful and even though he was very sick for 10 years, in my experience you're still never "ready" when it happens. You're missing the person, but you're also missing "what might have been" and you realize the days of making memories of your father are over.
I think mourning rituals and customs vary from community to community, from religion to religion, from family to family. From your remarks about "the temple" and the custom of visiting the house, I'm going to guess that you are Jewish. I am too so perhaps I can answer from that perspective and using your numbering system from above.
1. Some rabbis (and some ministers, priests, etc.) are not so good as pastoral care and funerals. Some, as in the temple where we belonged for years, are truly overwhelmed by funerals and hospice and pre-death visits, plus nursing homes. We hired a second rabbi (dual degree with social work) just to handle all of those visits; the senior rabbi did funerals for direct members, and the associate rabbi did all the hospital visits, the assisted living and nursing home calls, and the funerals for the non-members who "came home" for burial in the local cemetery. Even so, we had more than a funeral per week with an average of 15 hours per rabbi per family. It wasn't humanly possible to get to every person, and if someone else was doing the funeral, rabbis tended not to "take over". Next, did you respond to her messages? Did you have posted shiva/memorial hours at your home so people knew when to stop by? A lot of communities have gone this route rather than just expect families to have "open house" for weeks on end. Moreover, they may know your mother needs care and not just want to stop in unannounced. And a lot of non-Jewish people may not know the customs. When my MIL died, our non-Jewish friends often had never seen phrases like "shiva" or "memorial observance" and stayed away rather than do the wrong thing.
2. Everyone who wants a refund from camp or preschool or summer programs has extenuating circumstances. They may be under direction from the Board not to give refunds because they are operating at near-deficit level, and they can't fill the spot with another child at this late date. It may be the money that's bothering you, but it also may be perceived by you as a lack of compassion for your loss. I'm not sure that's the case even though I know it feels that way to you.
3. How wonderful that one friend checks in. The others may not know what's expected or desired from you. You say you aren't upset, but you are. So if you're giving them the feeling that you are fine (either consciously or unconsciously), they may be reading you wrong. Or they may be the kind of people who shy away from difficult situations precisely because they've never experienced it (you said hardly any of your friends have lost a parent). Maybe someone said to them, "He'd been sick for so long, this is a blessing." So now they think they'll make you more upset by bringing it up. And sometimes, sadly, in the face of tragedy, you find out who your best friends are, and aren't.
4. Your brother may be a loser (mine is), or he may be unable to mourn because he's lost all these previous years. He already feels isolated even though maybe it's self-imposed and a rift he created. I don't know. But he may be like your friends, not knowing what to say to the person who's been dealing with Dad (and Mom) all these years. So he may have guilt on top of his other issues. Guilt and depression and remorse can be paralyzing. He hasn't been around, so maybe you feel your pain is greater and he should be attentive now. Maybe you're right. Maybe he's not the sort of person who can face adversity.
5. You say your MIL couldn't care less but you don't expect anything from her and it doesn't bother you. But it does, a little, because you put her on your list.
6. Some people with Asperger's are high functioning and read SOME social cues. You're giving your husband a free pass here, which maybe he deserves, but again, it made your list so you're feeling the absence of help. Maybe you're not blaming him and are just showing us that there are all these people who "should" be supportive in most families, but because of special circumstances, you don't have that help in your family: brother, MIL, husband.
You sound like someone who does so much for other people. You have helped your parents in the past, and you want to take care of your mother now because she's not only lost her husband, she has Caregiver Exhaustion, and she's actually lost her "job" as the constant provider of help. That can leave her doubly bereft. So you're trying to give her attention and a vacation. That's admirable. You care for your husband in some ways, making up for his inability to do social things with other people. So are you one of those people who just give give give all the time, and other people get the impression that you don't need anything? I tend to be that way so I suggest it with compassion and understanding as a possibility for you.
We all do grieve alone in some ways, but many of us also are comforted by community. Jews have a 7 day period of shiva, but also a 30 day period of Shloshim. So if there are those who couldn't attend the funeral for one reason or another, or if you spent the entire funeral trying to attend to your mother and son and help your husband know what to do, or if you were still in a kind of state of shock, is there are reason why you cannot have a gathering at your home or the temple, with another type of memorial service, that would meet your needs? Ask your clergy member for what you need (she's left you messages, so take her up on it), and ask your wonderful best friend to help organize it so that it's FOR you and not BY you. We've done memorial services where the prayer book was used, but also with a time in the middle for people to share reminiscences of the deceased person. You can put something on Facebook or in the newspaper or in the temple bulletin. Sometimes people who come and share comments might be people who knew your dad, but they could also be people who heard stories from you, and they can talk about how they think you were influenced by him. It can be very comforting.
There's no timetable on grief so go ahead and call your clergy person, say you are feeling very alone and hurt, that you still have needs that were not met by the funeral itself, and that you need your community around you, and how can she help. Try not to organize the entire thing yourself, but just say what it is that you need. Then let the healing help of others wash over you. You can also ask your clergy member for helpful reading to do, but set up a couple of appointments so you can go in and talk (either about what you read or about what you feel). She's reached out to you (maybe not in the way or on the schedule you would have wanted), so there's no reason not to respond.
It's okay not to know everything you need at any given time. It's okay not to "get over" this right away. But if new hurts get in the way of your mourning, it will be even harder to heal.
May your dad's memory be a blessing.