In the old days, when I first came into the industry the global idea involved leaving a separation in between grafts. The concern was mainly grafts competing for blood supply. Thus, a patient would do a procedure and 4-12 months later he would return to fill in the gaps. To have a full set of hair, 3 procedures of about the same number of grafts was required. So, each procedure would do about 30% density. Further, a front would take 1200 grafts, the top, (middle area), would take 1200 grafts, and the back area would take 1200 grafts. Thus, if we were to apply this same concept to you.... a case of about 2400 grafts would give you that third procedure, and - by definition - fuller density....but....
You seem to have a very conservative hairline. So 2000-2200 grafts? Like I've told patients in the past, do as many grafts as you can afford - based on whatever the recommendation of the doctor is.
Something to keep in mind is elasticity. I realize you've done FUE...But a couple of things to consider. FUT is in play given you keep your hair on the lengthier side. You've had no FUT before so your elasticity should be intact. Typically the cost is less and you can always put FUE grafts on the scar in the future.
I would at least, so you can discuss all your options, talk to the doctor and see what he says and recommends.
Are you doing any medical therapy to help you retain the native stuff? Remember, if you've lost - you will continue losing. A shame to have to return multiple times to replace what you just lost.