You should use both a deck cleaner and a wood brightener after sanding before applying the TWP.

Probably okay.

I would apply after the stripping.

So how does one remove the old (oil based) stain? And how do you do it so that it doesn't damage any surrounding surfaces? (like the concrete/paint co...

I would look at the Armstrong Clark and 1 of the 5 gallon pails should be enough for all the wood.

Nope, you are ready to go!

TWP and Defy are old throughout the country. AC is a west coast stain that has limited stores on this side of the country. I would look at the TWP 150...

I am not sure that old stain will come off effectively. It is very thick! Try the RAD Stain Stripper to remove as much as possible then sand if needed...

It is already 15months old - do I need to wait longer?