momrk--welcome to the forum! Don't get discouraged, you'll both get the hang of it...
Here's my 2 cents:
Be careful what you use to clean the area with. Some soaps can leave a residue and that will cut the wear time. I use Dial (hate the smell but have never had a problem), some use Neutrogena and I think Ivory is okay too. His skin will be sensitive since you've had to change so much. Once he can get a day to two you'll see improvement quickly.
LESS IS MORE. Meaning that if you use too many products, you could cause less wear time. I don't use skin prep. It leaves a film on your skin and some wafers won't hold as well. You could also take the wafer tape off without remover (maybe not so close post op tho) by holding the tape and pushing the skin. Don't every try to pull off the tape...it will damage the skin.
I also use an Eakin Seal (in place of stoma paste). My stoma area is uneven and it helps to fill in the "low" spot and keep a good seal. It is just like stoma paste but it comes as a ring that can be moulded to the stoma's size/shape. I apply mine right to the wafer and then put the combination on. I also have a need for convexity (my stomach is funky with all the scars) not to mention my stoma is small.
The area around my belly button dips in a lot (I don't have one, just a scare) and has a wrinkle. For a while I would cut the wafer tape (almost half moon) so that area would be avoided. Once my skin healed I left the whole piece, just position it strategically. The wafer should still hold...just don't go too close the the important ring of the wafer.
You mentioned that the home health nurse has been helping you...do you have an Enterostomal Nurse you can get help from? It might be worth a trip to the doc's office to see one. I had great home nurses, but they don't have the knowledge and ET nurse does!
Please let your son know that in a few weeks he will forget all these problems!!! We've all had them and they are a distant memory now Keep asking your questions and mention to your son to join too!!