our girl is 9 1/2 months now. we had much of the same you talk about, and were basically exhausted. a few things that helped:
first of all: congratulations on having a healthy little sleeper - sounds like he's doing a good job learning to sleep on his own a little at a time.
here's some of my experience, i hope it's helpful:
a friend gave us the book 'healthy sleep habits, happy child'. while this was helpful in some important ways (mostly in learning to recognize drowsy signs), it was also really unhelpful (and even stressful - we finally just got rid of it), as our baby NEVER had a regular sleep schedule like the kids in the book, and believe me, we tried (even solutions you have decided not to try, which sometimes worked and sometimes didn't). what i ended up learning from this experience was that all babies really are different, that, unlike most of the books say, sleep is not a problem to be solved, but a rhythm we needed to discover together with our babe. we are continuing to discover it. i don't know if that helps, but changing the way i thought about it really worked for me.
we also got a miracle blanket, which is a special swaddle. they have a website. i highly recommend it. our babe was super active, but this REALLY helped (she worked her way out of every other swaddle), and she loved it. we also used a pacifier (something i was adamantly opposed to, but sleep deprivation is a form of torture, so...), and it was surprisingly easy to wean, as when she got too big for the blanket she started to pull the pacifier out and basically worked it out herself.
your baby will let you know what he needs, even if it sometimes seems counter-intuitive for you. as he gets older you'll see that he will often be leading you, saying, hey guys, it's time for a crib (or cup, or whatever). it's great that he's taking naps by himself for 30-40 minutes. our girl was like that. she never had those blissful 3 hour naps the books talk about. not once.
it's also helpful to remember: things will change. she started taking regular naps at around 7 months (she just did it one day, with no help from us, and then we caught on and started following more of a set schedule. so far it's worked great). before that she was ALL over the place. she NEVER napped for more than 40 minutes at a time. now her usual is about an hour and fifteen. and that will change too, of course.
there were times we let her cry, but these were because it was clear that she was exhausted and that our trying to sooth her was actually getting in the way of her process of getting to sleep. it never came from a 'we've got to let her cry it out!' place, but from a place of feeling sad that she was so tired and trying to give her the space to find sleep for herself. again, intuition based rather than book based.
one thing i really learned from the first six months was that sleep deprivation is just part of being a parent to the most wonderful little person in the world, and it's not permanent (though i think the wrinkles are!)
so i guess my advice is pretty basic: glean from the books but don't go by them, see sleep as a relationship rather than a problem, and above all follow your intuition and listen to your little guy. he's doing great.