Where do you stop?
Well I wouldn't have got anywhere near that far into it, even though I have the equipment to do so. I certainly wouldn't be fitting new rings unless the old ones were actually damaged, and would probably leave the bearings alone too.
Well normally yes, I'd agree. But AIUI James isn't trying to just get the car running again as quickly and cheaply as possible. He's treating it as a learning experience to help his recouperation and keep his mind active. So nothing wrong with pretending its a Rolls Royce or Ferrari engine, and doing everything "properly".
If the rings and bearings are good then re-use, but unless you check them you won't know for sure if they are Ok. Cyl #3 sounds like either top or middle compression ring is gone?
There is no info on the state of Cyl #1's rings since the valves didn't allow compression. So it's a risk to assume there is nothing wrong with the rings on Cyl #1. I accept they probably will be, but if they're not you'll have to strip it all down again (another CHG, set of head bolts etc) if/when you find out they aren't Ok.
So for the cost of a set of con rod bolts it seems sensible to me to take out all 3 pistons and check all the rings, pistons, bores and bearings. Look for damage, check the ring gaps, and use some plasti-gauge (couple of quid off eBay) to check the bearing clearances.