If your bank is useless, maybe consider changing banks. A new bank will probably incentivise you to do so, $5-10k or more depending on the mortgage level.
I banked with Westpac for 30 years, and they didn’t want to help me with a personal mortgage (as in, they wouldn’t make an appointment to discuss within a timeframe that suited me) so I moved across the road to ANZ who dropped everything to help me out, literally. And ANZ gave me $10k to do it, as long as I stuck with them for 2 years of personal banking.
As well as losing my personal banking Westpac lost my business banking as well.
As regards your account setup, I don’t know why people get too elaborate on revolving credits, split mortgages and so on. I would fix anything you can’t pay down, and float what you plan to pay down over the fix period, and review every time the fix period expires. Then keep business and personal cashflow separate. That prevents you dipping into gst/tax payment funds for personal spending, which is tempting for some.