We just did a family trip with our 2.5 year old and almost 3 month old. There were TWO of us, so of course that was a huge factor, but since I know I'll be doing it alone too (my family is in the midwest as well) at some point, I made mental notes along the way.
It sounds like you've done a great job preparing so far. We got our toddler a backpack of her own, and she felt VERY responsible with it, which was helpful.
1. Check the stroller at the gate. I have done this with all of our strollers (the cheap and the expensive) and have never had a problem. When you collapse it at the gate, get as close to the plane door as possible and ask for help if you need it. Yes, it feels stressful and rushed, but if you don't let your toddler see it-- it will be easier.
2. Potty breaks: let a flight attendant know that you're alone and that you may be asking for help. It seems if you are up front about your situation and friendly about it, they are more attentive. I've also had great luck with my toddler and other passengers offering to watch her when I've had to go while flying alone with her (I was 7 months pregnant the last time I flew alone with her and a 4 hour flight = lots of potty breaks!). As for their diapers, honestly, unless they're stinky, I'd just let them be wet until you arrive. If your flight is not full, and you have space along seats to change, that's a lot easier than trying to do it in those TINY bathrooms.
Something wonderful we experienced at both ends of our flights (last week) was the TSA now has a FAMILY line. If you are traveling with small kids, they have a different line, since it takes longer for you to get all the gear out, put it on the belt, etc. This was great because we didn't feel like we were annoying those seasoned travelers traveling alone.
As for tantrums, I'm not sure how much your toddler has flown, but we were very firm with our daughter about how she had a "job" to do and that mama and papa had jobs too. She loves flying, and airports, so she "gets it" so to speak. Keep your toddler well-fed, supply him/her with something new to distract, hype up the trip ahead of time.
You are so lucky you get to go home to visit! I know next year, I'll be taking a long trip home with my then 3.5 and 1 year old. Keep us posted on how it goes.
Best wishes for a wonderfully easy flight experience :)