Thanks, all! He was fine. (I was a wreck, but he was fine). I couldn't bring myself to wait until dinner, so around 3p ET I gave him a TINY amount of Weruva (he loves that stuff). No problem. I waited about 40 min and gave him a little more, and kept doing that until his normal dinner time when he got his "regular" canned. (Part of my guilt was that in barfing the tail, he also barfed up his breakfast, poor kitty). He was fine all night and doing well this morning. WHEW!
To answer your question, Lola, I have a vet's handbook for cats that advises to give 1 tsp of 3% hydrogen peroxide for every 5 lbs bodyweight to induce vomiting, but not to exceed 3 tsp. Since I was in panic mode, I used an actual teaspoon and probably didn't get enough in him in the beginning, but when I called the vet she suggested a turkey baster (LOL). I can do better than that -- I have syringes for when the kitties were on medicine, so that did the trick.
This is probably TMI, but a co-worker told me about this a couple years ago when her dog ate a bunch of chocolate. A friend of hers had done it and warned her to do it outside because it works fast, and it worked for the dog like in 5 minutes. I tried to do this in the bathtub but I think that kind of freaked Pookie out, so I let him wander around his usual areas and resigned myself to carpet cleaning duty.
On the bright side, at least I was home and saw him do it. Sigh . . .