How to insulate my circa 1940 brick and block garage woodshop . . .

Hey all. I’m an LJ guy sneaking over here for some free advice. I’m certain this topic is probably covered in a lot of places here, but I haven’t been able to find my specific circumstances addressed. I have a woodshop in my detached, 70-year-old, 20×8, uninsulated garage. I’ve made due for a couple of years with box fans and an electric heater but I would like to begin spending more time out there and need advice on insulation. Let me preface my questions by saying that I am NOT looking for an elegant, super energy efficient, perfect solution here. I am looking to do the minimum necessary to be able to spend more time in the space when the weather has a different idea in mind, without causing any permanent damage to me or my garage.

The garage is constructed of brick on the outside and hollow block on the inside. It has no attic – i.e. it’s open to the roof. 85% of one wall is sheathed in plywood to be able to hang tools – the rest of the walls do not have a covering. The garage door is uninsulated. There is no ridge vent, nor are there gable vents. Soffits are not vented. See attached pics. I am thinking of installing a mini split heat pump to condition the space. Good idea or not? If it seems feasible, these are my insulation questions:

Can I install batts on the roof underside without risk of condensation issues?
Can I sheath the rest of the walls in plywood (I am using 3/4” furring strips)?
Should I insulate the gable ends? Batts ok?
Foam insulation board for garage ok?

I’m no builder or tradesman – just a intermediate woodworker – so please steer me in the right direction if my ideas on this are not going to work.

-- Just make the cut . . .