4. Can you please elaborate on what issues you think we will encounter when we go live?
Probably the deposit and the crediting, you should test it yourself and not do this in public to make sure the deposit, crediting, and cart are functioning properly, the worse thing that could happen is getting bad feedback or complaints for not functioning features
5. Manual deposit and withdrawal at this stage. We are trying to avoid using third-party systems.
If you're going to implement a cron job and it will work properly then it's better than getting a third party.