Is there a way for me to see which pet has my apparels, similar to how I can view which pets have my custom skins? (if no, I'll probably make a suggestion if the admins haven't read this.) 

Also, I'm not getting a notification for when someone uses the apparel (as with custom skins). Does the silver go to me or just disperses back into the game?

Currently there's no way to see the pets with your apparels. An apparel is a bit more ambiguous entity than a skin. It may exist as an item in player inventory and as an item in pet inventory without that pet actually equipping it.  

The fee works the same way with the custom skins and goes to your account. But yes, there was no notification. We just added it.