I have seen many 6v cars using battery cables appropriate to a 12v car, too small. Add in some crusty connections and it's problematic. Rockauto sells new battery cables of the right size if you want to go with new, yours look to be 6v cables though,
I usually put a thin coat of antisieze on them.
It's a bypass filter, they work, after a fashion. Some have modified the oiling system to use a full time filter like on modern cars.
Common setup back in that era. Probably needs adjusting, the manual should help.
The brakes need regular adjusting, not knowing how long it's been since then might be a good idea to do that. The puller is readily available and not too expensive. Some have been able to loosen the axle nut a couple thread, put the cotter pin back in and drive it around the block a few times to pop them loose. I have never had 100% success with that.
They do that, the road draft tube is a source.
If you are use to rack and pinion steering, most modern cars, it will always feel loose. Keith, on this site, has a pretty good write up on what he did to rebuild his, a video too I believe, Not likely to find a reman though, the steering column shaft is one piece all the way thru the box.
I'd change the trans and diff fluid, so I start from a known point. Probably flush the brake system too, I have a post here detailing a power bleeder I got from Motive that makes it a snap,
Nice looking ride. Those cars are a lot more maintenance intensive than newer ones. You will have dozens and dozens of grease fittings to lubricate. I bought a cordless grease gun just for that.
The site has a lot of info, the search function isn't the best though. Poke around, read up, ask away.