So, this post is just screaming for feedback. Hope you don't mind the dissertation to come, and that it actually helps.
First and foremost, good catch on the trends you identified. The occasional shoots that were dropped seem to be coming out low and left of the target. I would recommend you checking (by feel) the amount of grip pressure you are using, dominant versus support side hand. You want to have more on the support hand side than you have on your dominant side. That patter of shots, to the left, almost always means that you need to increase the amount of pressure on your support hand side. That will almost assuredly bring those dropped rounds back into the desired point of impact.
"As I have stated many times I am far from fast and not always accurate" - as for this statement. Believe it or not, this and other thoughts like it (even if said in jest) have A LOT to do with performance. Essentially, if you want positive results, we need to feed our brains positive thoughts. YOU have plenty to be happy about from a marksmanship perspective on this drill. You finished all of the groups well within the par time and your best run was a clean run at under 4 seconds. Believe it or not, the average gun owner/CCW carrier is not capable of that level of performance. You have a few things to polish up, we all do, but you have NOTHING to be ashamed of. You, in fact, are fast and accurate, don't sell yourself short.
As for the timer, you can do both. You can either set a par time to let you know when the 5 seconds is up or just go off the last recorded shot. I prefer the latter myself. I almost never set a par time in live fire, only when using the timer for dry fire. Great question though!
Hope this feedback helps out some. I look forward to you seeing some progress and nailing this drill later this month!