#4 may be connected with your switch configuration. Normally you’d keep the batteries separate, using engine battery for starting (only) and the leisure/house battery for everything else. Most boats have the ability to connect the batteries together (to allow starting if the engine battery is low), but if you accidentally leave them connected, then using fridge, lights, etc will drain BOTH batteries, so you empty the engine battery too.
Re #5 – try spraying the luff groove with dry silicone lubricant. Even from new, I had to winch the last couple of metres of my GL350 mainsail halyard, unless someone at the mast “sweated” it. I also connected a light line to the top of the mainsail, routed down the mast, through the organisers and along the deck to the jammers inside the sprayhood. That was very useful for pulling the mainsail right down to the boom (it didn’t drop all the way under its own weight, with sliders and only a couple of cars), and also handy to lock it down once dropped.