It may be worth investing in some hardware like a knob or bluetooth keypad to get a couple shortcuts back. Knobs are super handy because it allows you to dial in parameters on the fly, like stroke size. I also map controls like undo and deselect to the extra buttons on wacom drawing tablet. If you have a button on your stylus, it should map to a popover menu that provides access to most common controls.

Finally there is also a hot key to hide and show the toolbars (Canvas Only mode) that may be useful. It's keybind is Tab, but the documentation says a 4 finger tap on touchscreen will activate as well. Might be worth investigating.