[Gunter]

Kurt,

Partial lowered and some parts removed to make room sounds good so far; try the easy stuff first.
A good indent ground into the pin with a Dremel will help. I'll keep the center punch and/or drill centered.
Try a good-quality center punch first but I found that the hardest punch was one I made from a small round file. Expect the tip to round off fairly quickly.
I would use a few drops of penetrating oil (NOT WD-40) on the pin before hammering.
Real penetrating oil will creep into the hole and help free the pin.

Try to hammer the pin to the opposite side of the shear-direction.
If the center punch slips too much, I'd make a chisel from a small flat-file, grind the front edge flat, set the smaller edge into the side of the pin and try some careful hammering with the chisel at abaut 30-45 deg.

Bragging about how it all can be done in record-time is beerhall-talk.
Have patience and be careful.

If it comes to using premium drills, I'd try to use the rear bumper as a way to apply a little pressure on the drill motor so the drill can bite. It's a careful balance between enough pressure but not too much so the drill doesn't break. I'd first drill the existing hole in the old pulley right through. Then I'd install the pulley aligning it so the through-hole sits exactly over the pin. That way, the pulley acts as a jig to prevent the drill from wandering off.

The best advise for welding comes from JW, IMHO.

The hole in the crank is not a through-hole. Another hole for a new pin will have no great effect on balance but, before drilling a new hole, I'd consider a slightly larger O.D. in the existing holes for an over-sized pin.
The big bolt is high quality and if it's not damaged, consider re-using it.