The thing with guillotines is you'll almost never catch someone in them that knows what they're doing unless you have it really, really tight with your guard closed in. The counters are just way too easy and effective. Also your arm's probably just hyper extended and should be fine in a day or two.
Also I've been working on my striking a lot, my one-two is getting pretty nasty and I'm getting really good at slipping jabs/crosses and creating angles.
Anyway probably the best thing you could do for your grappling is remember, position before submission. I never really took that to heart til I got out pointed at the tournament, and it's worked wonders for my ground game. Of course I still will go for subs from the bottom if I see an opening, but my sweeps have gone from non-existent to really good and my overall game is a helluva a lot more dangerous. It'll especially benefit you if you like striking, since even from someones guard you can land pretty good strikes. Work on your sweeps, trust me it will pay off.