As for filling the holes: instead of a torche and inhaling melted plastic fumes: you could use acetone and plexiglass. Cut up some spare plexiglass scrap and pour in just enough acetone to cover it. The acetone will totally dissolve the plexiglass and leave behind a sticky liquid. The viscosity of that liquid depends on the ratio of plexiglass to acetone. This sticky liquid is essentially a plastic cement that will leave behind nothing but plastic when the acetone evaporates away: allowing you to do chemical plastic welding. You can get much stronger and tighter bonds, especially if the plastic you're bonding to is also dissolvable in acetone. There's commercial products that is exactly this mixture. But it's easy enough to diy. I discovered it when I was a broke college student making some fun art projects with plexiglass.
