Thank you for the hard work. Reading this 'long lost' piece of wushu masterpiece is a great pleasure. My initial exposure to the story was from the 1980s TVB's adaptation by Tony Leung and while I knew that there were differences between the original novel and TVB's adaptation, I kept on expecting some of the adaptation's plot to unfurl. When the story ended, I kept coming back to see if it is actually completed as the plot by TVB is different and I had hopes of a great battle/final showdown.
Anyway - the TVB's version goes this way (my memory is hazy):
SPT and the rest came back to the mianland. Before long they realised BeiHaiShi has taken over the Wulin. XieYanKe was helping him too. SPT and gang cannot defeat BeiHaiShi. They retreat. SPT's father was killed by BHS - smack on the head while holding onto BHS's legs to let the others escape.
The plot unfurls about how BHS got so powerful - initially when the 2 island's rulers came to invite the Shaolin Abott, they brought a single piece of the stones to show the pugilists. At shaolin, one of the young monks decided to secretly follow the Abott. When they were going to the island, he shuck up onto the ship (undetected by the 2 island masters and others? v. suspicious). The ship met a storm and the stone and young monk fell over board and he held onto the stone while he was blown back to mainland. The ship proceed to the island. (EDIT: BHS is the young monk) From the stone he managed to deduced the rest of the exotic martial arts (like SPT). He plotted to get rid of most of the powerful ppl in wulin by murdering some of the ppl and making it look like Zhang San and Li Shi's work. He also waited for the leaders to goto the island before launching his attack to take over Wulin (maybe he's worried about having to deal with so many people).
Someone in SPT's gang thought of an idea - SPT will pass his new martial Arts onto his twin brother SZY (revealed much earlier - not unexpected anyway). And so they train up and challenged BHS. BHS is defeated in a final fight tthat is quite disappointing in terms of special effects. SPT and SZY splitted the ladies among the 2 of them: The 5 poison clanleader, that maid, the XueShanPai grand-daughter, DingDang, there might be some more, I cant rememeber. Good life. The end.
EDIT: XieYanKe is a nicer person than in the novel, he truly cares for SPT treating him as a companion as he has a lonely life. XYK helped BHS because he felt that there was no way he could win him but I recall he let the 'rebels' escape or something. Can't really recall his fate... dont remember him as a traitor/bad guy.