Ok, take a breath. You're all over the place so it's really hard to get a grip on what the heck you are saying.
1) "Turning over" means 'cranking' (battery), and "starting" means 'running' (fuel/spark). Very different systems to diagnose.
2) Yes, you should replace your spark plugs. Starting it repeatedly and not riding it will certainly foul your plugs fast on a Buell. The Buell Rule is if you start it, RIDE it. You won't be riding this one soon, so DON'T START IT. See #7
3) You don't need a wiring diagram to put on front signals the wires are behind the windscreen, the diagram is in the link I already gave you. Strike one for not clicking it. RTFM. BUT. Why would you even consider buying fancy black parts for a bike that doesn't even RUN??
4) Engine removal instructions are in the manual. In the link I already gave you. Strike one for not clicking it. RTFM.
5) If you are able to remove the engine yourself, the least of your worries is how to spin it over. You will disassembling it anyway, why dick with the cumbersome rear wheel hanging on it? It is one large bolt to remove it (and a pinch bolt). Same for the swing arm.
6) FIX IT. FIRST. We will help... BUT, there are several things you need to be familiar with that are in the link I already gave you. Strike one for not clicking it. RTFM
7) In your video it looks like the head bolts are loose or stripped letting blow-by creep past the cylinder base gasket. Not good, but also not catastrophic. IMO NO, don't ride it. Every power stroke is trying to lift the cylinder out of the case on compromised bolts. If they are just loose now, they will strip out of the case if they are ignored.
8) Yes the oil pressure light is on with the engine not running. There is no oil pressure in an engine that is not running. Thats why the light is on. No oil pressure. It's in the link I already gave you. Strike one for not clicking it. RTFM
9) NO, I would not JB weld a cylinder to a case. It won't hold the cylinder, it won't seal the blow by, and it will be a nightmare to remove.
10) Its 'brakes'. If your brakes break, fix the brakes. Then take a break.
If you want to ride this Buell, you have 2 options:
1) Get it started and ride it until it breaks. That will be soon.
2) Fix it. IMO, that means rotating the engine and re-torquing down the head bolts at the least. Most likely you will be removing the engine, removing the cylinders, and repairing a stripped case.
Depending on what you find, and how personally deal with the dreaded 'might-as-wells', that can be an easy job, or a never ending saga of time and money. Personally, I love working on bikes and would do the minimum to repair it properly, meaning repair it, NOT modify it with unnecessary and expensive engine parts.
You could find tight head bolts, (remove the cylinders and replace the base gasket).
or
You could find loose bolts and good threads, (remove the cylinders and replace the base gasket)
or
You could find stripped head bolts, (remove the cylinders, repair the threads, and replace the base gasket).
or
You could find a trashed engine, (split the case and repair, or buy another one).
None of those possibilities need a stroker kit, transmission, chroming, turbo, or black turn signals.
Good luck buddy:eagerness:, if you choose to take this project on there are plenty of sources for good information, but I won't be typing a step-by-step copy of the manual I already gave you. Let us know what you choose:angel: