I think UTI is a possibility, skin problems are a very high risk.
I have to tease you -- are you really sleeping 10 hours?!
I wish that I could sleep that long.
In addition to changing the belly band more frequently, his belly needs to be washed and dried. Even without belly bands, my guys require fairly frequent belly washes to stay clean and prevent problems. They have "pee strings," hair to direct the urine away from their chests.
Hopefully some belly band users can give you some more tips.
When you can supervise, work on training more with the pad by limiting Boomer's roaming room to a smaller space with the pad. Limit his freedom when you aren't there too. Make sure you praise and reward when he uses it. Also, change the piddle pad frequently. Sometimes dogs will not want to return to pad if they think it is getting too used.
Clean up accident spots thoroughly with an enzyme cleaner to discourage him from returning to the spot to do it again.