Rachael, throbbing needn't lead to spasms. I've had some throbbing on and off, when I over-do things, and none have led to spasms. I don't think I've had spasms for a year now, nor the broken glass feeling. I'm sure throbbing is really normal after a cut like the one you've had.
Also, the reduced pain/more pain thing - again, I think that's incredibly normal. I've not had LIS, but that was true of my healing. It's going to depend so much on your stools, their hardness, their acidity, their frequency. Also whether you are resting enough.
Give yourself time and try not to worry. I don't know about you, but anxiety makes me clench my bottom - NOT a good idea! Baby yourself, and stay positive. It really does help.