i wanted to let him alive but it was my first (blind) playthrough and I failed the quest after that i failed catarina too, should i restart the whole game?
If you want him for the final boss, then yes. However, you are likely to be near the end of the game, so I would suggest to try out Gwyn on your own first.
I got invaded yesterday in Anor Londo when I was kindling that one bonfire before O&S. Invader used Solaire as a cover and i accidently hit him... I lost this invade, I lost my beloved Solaire, I lost everything and now I'm forever alone in the dark...
Talked to him in undead parish And he isn't in anor londo(still avaible for O&S) Killed all chaos bugs via izalith shortcut but he isn't in centipede demon bonfire Bug or ....?
You don't need to kill the bed of chaos in order to make him spawn, but u do need to kill the centipede otherwise he wont spawn in the hallways where the maggots are at. After you kill the centipede (do not go further then that bonefire, do NOT trigger lost izalith) warp back to daughter of chaos and do all that shortcut thingy, kill the maggots and go up the stairs towards the direction of the titanite demon then head back without needed to reload the area or anything and he will be sitting there.
There are only 2 situations where I find wearing his armour agreeable:
1. You failed his quest and killed him in Izalith, and wear it out of respect 2. You killed him in NG, bombrush to NG+ to get him back, and wear it then, as we all know that impersonation is the greatest form of flattery