Okay Alex, but the number three looks somehow.
3. If admin can not deduct money from users fiat wallet then is really something to worry about, if an admin can manually credit a user from the backend, lets say admin credited a user $2000 and discovered he made a mistake and the actual amount he should credit the user is $1000 not $2000, how then can he deduct the excess of $1000 from the user balance? So there must be a way for adding or debiting a user fiat wallet balance from admin.
If you look at yith woocommerce account funds plugin you will discover that an admin can adjust user balance. You add and also you can subtract from user balance and this makes it okay, just in case.