Well, your plan sounds good. I've never done rack pulls since our gym doesn't have the equipment for it, and my deadlift is still increasing nicely, so I personally don't feel rack pulls are essential at all. I've also never tried pulling from a deficit, maybe it's something you could try to bring up your strength at the bottom portion of the lift though.
If you are struggling to increase the weight using singles and doubles, do more reps for a while, even around 10 reps would not be crazy. Work your way back up to around your old max, and your new max will be higher. I can't recall whether or not you said you're doing 5x5 further down in the thread, but that scheme didn't work well for me.
Increasing bodyweight would help, as would doing some heavy work for hamstrings. If there are parts of your form that you're struggling to get right, I feel it's easier to correct one thing at a time, instead of trying to do it all at once. Within the past couple of weeks, I noticed concentrating on keeping the bar really close to my legs helps a lot (that's a form issue I had, I guess).
Try deadlifting every 2 weeks instead of 1 - assuming you are doing it once a week as most people do. I don't think you would need to deadlift less than that to see progress at this stage.
If you need to use straps to do a rep, use them.