frustrated 4runner

hello,i hope someone can help,i just bought my 91 4runner,and it has problems,first if i let it sit to long like 5 hours or so it wont start,have to jump it,my headlights are not dim or yellowish like,the amp gauge in the instrument panel is goin over 18 volts,not sure if i can trust that,had the battery tested but they didnt no if it was bad or not,next when i left the parts store my low beams made a bright flash and quit working only my high beams worked and when it did that my windsheild wipers came on,and i have a wire that goes from the positive battery terminal to the fuse box beside the battery it gets hot so hot you cant touch it,i think i have a short or bad ground but dont no where to start.also the old owner put a push button in it to start the truck,and you have to turn the key to on then push the button to start it,i could write a book on here with the problems im having.and when i press on the gas peddle my dummy lights come on the warning lights in the instument panel,the engine has no power rough idle goes 0-45 in 4 minutes yea its slow

Unfortunately it sounds like someone who had NO BUSINESS altering wiring has done just that to your vehicle.
You will need a god set of schematics, I recommend ONLY the service manual schematics as I have uncovered gross inaccuracies in the aftermarket Haynes magazines.
You will NEED to correct the wiring before trying to uncover why your voltage regulation has damaged components.
No wire should ever be warm to the touch, if it is, and is connected properly the gauge of the wire is too small.
The wire that was getting too hot should have opened a fuse. Never shunt fuses especially with a vehicle that has modified wiring schemes, it is a quick way to lose your entire vehicle to a fire.

Install a meter inline with the main supply link, (the wire that is getting hot). Then pull all the fuses even the mains, start inserting the fuses and watch the amp meter you should uncover the circuit that is drawing the current.

thak you for the help i fixed the hot wire it was loose and the wire sizes were differnt and couldnt handle the flow if that makes sense,but i have a lot more work to do like you said wire it back to stock some people just dont xare if they mess something up if the car runs ill keep ya psted thanks again