Drain the water down a foot, that will give you more area to heat and get the stretch you need. You need to get it hot enough that you can not use bare hands to pull on it. You need to come up high and in, not just high flush to coping and in . If the rest of the liner is holding water and your happy with it it seems a shame to spent the money on a new liner.
I do not like the looks of the liner around the skimmer. Looks like something has moved but i do not see where. The left side makes me think this. Thinking i would lower the water below the skimmer and maybe remove the trim to see what is going on there. I do not think you will pull the liner up with the trim in place, the best you might get is like it is on the left side in the images.