!) Yes I agree you should have nothing to do with the donations at all and you need to rectify this as a matetr of urgency and open an account linked to ************ which then feeds into the main fund -
2) Yes these must be audited and examined independently annually
3) I am afraid this is a finance/banking issue and we are UK tax experts - you would need to discuss this with the bank but usually the treasurer alone has access to the bank side of matters - but through my experience of having been treasurer of a charitable club, I do know its just cheques when written do need 2 signatories - so therefore just clear this with the main trustees/committee at the next monthly meeting re online banking, printed statements and a secure location to store them.
Let me know if I can assist further