Wont list any spoilers but basically right at the FINAL planning (All items collected, people killed etc) Cant seem to make the quest activate.... Im stuck with a quest log telling me to wait for the dude to find me... Im on PS3 version, so no console commands... I want to be a master Thief and I CANT!!! so annoying.

Also, I lost my horse from the end of the assassin quest line.... hes gone, disappeared after I fast travelled for the first time...

If you lose Shadowmere, return to Fort Farragut and he should be waiting there. If you armored him, though, then he may be gone forever.

As for the TG, you don't really have much choice but to wait for them. Try in different cities, they may have wandered off to Anvil looking for you or something like that.

Same thing happened to me, I waited in every district of the IC for a week, and then in every city for a week, then in the wild for a week, then back in every district of the IC for a week. Still hasn't come