Radiant - I was exactly the same when I caught my ABF using drugs. He claimed that they were alright because they were legal highs but they're actually worse because you have no idea what is in them and the stuff he was using was strikingly similar to cocaine. You feel a bit of an idiot and naive because you believed what they told you, when in fact, they've been sneaking away doing these drugs. My ABF was always disappearing for a good ten mins or taking longer in the toilet than usual and I never clicked until I caught him with a packet of the stuff at my dad's birthday party. I lost it and told him if he done it again, we were through. As far as I know, he hasn't but that doesn't mean that he won't if given the chance.
Meth is a far stronger drug though and as everyone has said, people can destroy their lives in a matter of months and they'll drag everyone with him. Good for you for getting him out, changing your locks and moving in with your own life. You are a fabulous person and you do not need people like that in your life! Things like fixing household problems are such a big step for us because we know that we can fix it ourselves, we don't need no man to do it for us! Ha ha!
Big hugs to you, brave lady! I wish I had half your courage!