Instead of focusing on getting tighter groups, focus on getting a good feeling shot. That shot where as soon as you take it you go "ohh, that felt good." There's a ton of good advice on here but keep in mind that tight groups really aren't the goal, they're the bi-product of consistency. When shots go wild, ask yourself what was inconsistent with that shot form the time you draw the bow till the arrow hits the target. What about that shot didn't feel or look good from the shots that do?
Trust the pin float. If that pin isn't moving, you're going to mess things up. Slowing the float down with a stabilizer that actually stabilizes your bow helps there, but you don't want the pin to ever come to a dead stop. Get the consistency down and groups will tighten up. Once the groups are consistent you just play a trick on your brain and move the sight. You're brain will be wired for the consistency and adjust to maintain the consistent sight picture.