Thank you everybody.
Concerning foul hooking the fish, well, of course I cannot guarantee it was not the case, but I try to do everything I can to avoid that. First cast, I estimate the depth of the pool, if the float is bouncing a bit (touching the bottom from time to time), I put my thumb on the spool to allow my leader to come near the surface and then gently reel. I then lower my float at least one feet and cast back.This way, I very rarely snag the bottom and I think I decrease the chance of foul hooking a fish. The two spots were I hooked the fish I had a problem to control, I knew I was way above the bottom. I casted there and the float stayed straight in the water during my drifts.
One of my problem, I think, is that I give too much liberty to a fish I hook. I am still not used to hook such big fish and I have some problem to estimate the resistance of my leader and I give line too easily to the fish. I konw it is bad, because the fight last longer and I probably tire the fish too much this way.
I usually try to pull the fish in the oposite direction I want it to go, and it works for a while but I still often end with a fish running in the next pool.
I asked the question concerning the wool, because I have heard that wool is often the ticket for salmon (if you exclude roe of course), but I had more success using a small spin n glow or a gooey bob. If it does not work better than anything else, I do not understand why wool has such a good reputation when it comes to salmon fishing.