Dad playing with the throttle didn't cause any problems. I do it all the time with fresh engines. Especially when pumping up the lifters, 2000 rpm is usually good to get the oil flowing.
From your last post and the first with the updates, it appears you don't have oil pressure light on any more, no more odd electrical issues. Those are good. I'm not sure if the oil level issue has been corrected by the grounds as well. IIRC all those items are based on those two grounds and should be good now. BTW, that's a super easy item to miss... totally acceptable for a first timer and now that you know it.. you'll never do it again. Next time the wire will break off the eyelet, but you'll know where to start.
I would probably do a compression and leakdown test for starters. Make sure things are good with the rings. Usually at high mileage you can still see cross hatching in our cylinders and the rings look fantastic for the milage as well, but it's a cheap easy check.
On the oil burning. if the smoking is getting worse, I'd think it's valve seals. These motors don't typically burn coolant. Heck a horrible looking LIM gasket usually isn't even leaking into the crankcase. Overall they look brutal and don't cause an issue that you'd equate to how serious the gasket looks to be compromised.
I'd grab a set of valve seals valve cover gaskets with grommets, LIM gasket, maybe a set of 105# springs, modded retainers and reusable bolts. Do the valve seals and swap the other parts, in the case you ever decide to put rockers or a cam in, they are already for the install. Do the LIM gaskets at the same time and you should be all set.
Then down the road when your confidence is good, you can toss on rockers w/o thinking about it.
