I went through major abdominal surgery during my pregnancy with my 4th, and you have to have someone to call on when you need them; another sahm, or a close neighbor. And you have to learn to let a lot of things go, and childproof like CRAZY. If you have a child proof area, it lowers the amount of picking up, you just have to deal with the mess (which you shouldn't be picking up, cause bending is also not so hot for stitches!)
My other little guy was 3 when the baby was born, and he turned into a great little helper, since I made sure to play up how special he was - not as my baby, or my big boy, but just cause he was my "one & only" (then his name). I recommend that.
I would suggest trying to move his naps around from when they are. If he falls asleep right after lunch, try moving lunch earlier or later so that you can catch him tired for his nap in bed. If he's really hungry, try giving a "special super nap snack" (something that isn't crumbly or messy) to him as you two sit on his bed, maybe under an extra sheet like a tent - with a book, then if he passes out, you can either ease him under the covers, or just use the tent sheet.
Unfortunately, the meltdown thing seems pretty standard 2 year old fare - it takes a lot of restraint, but if he's somewhere relatively safe (living room carpet) you could try just stepping away so you can't see him (or more correctly so he can't see that you can see him). Once the audience isn't looking, they tend to end faster. It takes a lot of self control though, I've got four, and I've only been able to use that on the youngest two... Sometimes with some kids, whispering quietly works, they stop to hear what you're saying.
Best I can tell you is pick a mom friend - a REAL mom friend that you can run errands or go out with, that way if a meltdown occurs, you can trust that she will do the heavy lifting.
And most important, remember that you don't have to be the perfect mom. You have to be a LOVING, CARING, good enough mom. Cause that's what they remember.