There is no Dina Card processor in Serbia so customers should pay me 30% deposit into my bank account and the rest at arrival. I make t-shirts and if customer wants something not in offer, i take deposits to be sure he will take it

1. Can customer pay me ie $200 in my bank account and when i see the money, i would give it into his account? Then, at checkout, 30% would be deducted from deposit and the rest would be payed at delivery?

Example:
Customer gives me $200 (on hand or via bank transfer). I set his account to show that value.

He buys something for $100. At checkout, $30 would be automaticly deducted, $70 he would pay at delivery and $170 stays at his account

2. Can his deposited money be visible all the time?

3. In case this is not possible, can it somehow, at step 3, be shown that 30% of total has to be prepaid (of course, and how much this 30% is) at xxx bank account and the rest of 70% (and value in currency) to be paid at delivery?

4. Can this be attached to just one or two products? Ie. for all the products, standard 'on delivery' payments are used. But, if he orders something that yet has to made according to his wish, only the above method should be used.

I believe it would be new payment module but i couldn't find any that would match what i need. Nor on forums.