Oh boy.....better hope she becomes reasonable, it can go pear shaped quick.
Tell him never lose his cool, and if it becomes difficult, better see a solicitor.
All accounts should be both to sign, inform bank of the split.
Banks do not care who pays, but both are responsible to pay the loan, your not contracted to pay half, but the whole amount.
Please update every so often with result, and remember, there is always someone in a much worse position.