I know you'd love to get some more life out of the boat, but right now, unless you've got an inexpensive glue source and LOTS more time than money, or you just are fired up about this, you're throwing good money after bad. I've heard of a raft repair man rebuilding a hypalon boat by turning the whole thing inside out and reglueing all the seams, and everything, but this is pre-1988 PVC we're talking about (IIRC, after '88, Maravia was coating all their boats with urethane). If you look around at this time of year, you should be able to find something decent for $1500 or so.
Nothing in the world is more yielding and gentle than water. Yet it has no equal for conquering the resistant and tough. The flexible can overcome the unbending; the soft can overcome the hard. - Lao Tse