The HLTV event doesn't get called for each player separately, it gets called only once and there is no player ID passed to the function. This means you need to set the whole array to false at once,
arrayset can help you with that.
I don't know about the issue with sizing though, it looks fine to me. Not sure how big your tree model is, but 50 units is still not that much, so if you have a big tree, it might seem like changing from 1 to 50 isn't doing a lot.