Answers

I would remove paint. Corn blasting and Osborn brushing usually works best.

Inside, a couple of weeks. Outside, a couple of days.

http://en.wikipedia.org/wiki/Sandpaper

Not that I’m aware of, unless you buy a roll of sand paper and do it by hand.

First, never use paint on wood! You want to use a latex semi-transparent stain made for log homes. I like LifeLine. Call 800-564-2987 for help and to purchase.

A long nose belt sander may work.

Sure, but do not use epoxy, apply Shell Guard borate concentrate.

Use a latex based product. Sounds like the product you are using is linseed oil based.

You will probably have to sand it, but it may require the entire wall if you can’t blend the spot in.

I would say talk to a window company, but I would make this companies liability insurance pay for it, if they have any. They obviously do not know what they are doing.