At first, the no-shoot number is 200 (with human meter), but as you gather data and learn your cat, you can begin to shoot at lower numbers. There is definitely some trial and error, so testing becomes even more important. You shot 3u when he was 186, and you saw that that was too much. So, next time, maybe you try shooting a smaller dose when his number is in that range and see how he responds to that. You have not gotten any PM mid-cycle tests, so it is hard to see the full picture of what is going on with him. You may want to start trying to grab some of those to help you as you have to make more refined dosing decisions.
I agree with you not staying on 3u. 2.75 may even be a tiny bit high since you are seeing the big differences in pre-shot numbers. I might try a 'fat' 2.5 and stay with that awhile to see how he responds... also shooting it when he is a bit below 200 to see how that goes.