A few minor scratches won't make a lot of difference. Unless you are trying to print at sub 0.1mm layer heights - or looking for a mirror smooth finish to the bottom of your prints I doubt you would even notice the dints.

I have found that a butter knife works well, with a flat bladed craft knife for any really solidly bonded bits. I use Print Tak on top of the standard stainless plate and I am 500 hours and quite a few prints in without any serious issues. I find a sheet lasts about 40-80 prints - so long as I look after it. In fact, the last one was changed as it had picked up a sticky residue and everything was sticking to it! Trying to work out what it was, as I reckon I could get grease to stick to it