Forgot about save files. They work for me. If you don't want to lose your saves, never delete your cookies. If it still doesn't works, try to play using Firefox.
SFH3 is quite buggy and it has some really OP weapons like Crazy Badger. Just used one lvl 8 Crazy Badger to complete all missions on hard. And about bugs: when a character reaches lvl 30 his xp bar fills more and more, until there in no space on your screen or when a 94-97% accuracy sniper rifle misses lots of times when you're aiming exactly at your enemy's head, but SFH3 is still playable though. About lags: yes, it may be lagging a bit, but I'm playing from an quite weak PC, so idk why you're saying bad things about SFH3. Maybe because West is still dead and Dex is alive... idk