Your considered Xuron PE scissors may be overkill. I've found a very effective tool for removing PE from the fret is a plain old #10 Xacto blade (the rounded one) on a piece of hardware store bathroom tile (49 cents). A #11 blade is useable, but the point breaks easily on the tile. Put the point of the #10 blade beside the nubbin which holds the part to the fret and press/cut in a rocking motion. I've found that a piece of dark tile, as opposed to white is easier to see the PE against. You can put the whole thing in a large zip-loc bag to minimize the part from flying into oblivion when cut. The choice of spending your money on a specialized tool or on a general one which functions as well is up to you.
The smooth-jaw pair of pliers is a good choice.
As far as a special file to remove the nubs from PE, instead of buying something with a model manufacturers logo, consider something which is widely available. My favorite tool here is a sanding stick from Sally Beauty Supply. They sell them as nail files. A fine to extra-fine grit does the job. They cost less than a buck -- and I got a 5 dollar off coupon in yesterdays mail. I'm going to replenish my stock this weekend.
Your 6-inch steel rule is good. Another thing to look at is a 3 to 4 inch scraper blade in the paint department at the hardware store. The Hold-n-Fold people used to include one in their tool, but you can get extras if you look around.
Another item you might want to look at is glue. I use Aleene's Tacky Glue from the craft store to tack the parts in place. It grabs quickly, yet allows time to reposition the part as necessary. It is water soluable -- so cleanup is some water on a Q-tip. After you are satisfied with the position, then commit to CA for permenant attachment.
For measuring, a pair of draftsmans dividers is excellent. Adjust the thumbwheel to the correct spread of the legs. Then use that to transfer the measurement directly to your part. You don't go through the process of guestimating from a ruler - then transferring that to the part to be cut.