First off all, if you choose path d at samantha wedding lp will lock at 75%, but if you choose path b you can increse the lp. Here the walktrough for sam wedding :
1. First, caught ryan cheating at nightclub
2. Dont tell samantha about ryan cheatinf until samantha wedding appear
3. If samantha wedding has appear, dont tell samantha about ryan cheating, you can go to bathroom and caught ryan cheating with natalie (the briesmaid)
After this i dont remember because long time i dont play this game xD