Great!! Didn't you say PO4 was undetectable? You may hit "absolute zero" PO4 if you dose NO3 without also adding PO4, and that would be very bad. The pellet approach may help this situation though since pellets are high in phosphate, just be aware it could happen. I have nitrate dosed with great success many times, but when I tried it on my current reef about a year and a half ago, I hit absolute zero PO4, and it took months for the Acros to recover.
Are you still adding any bacteria/NP Pro or using any other nutrient reduction resins/medias/liquids/etc? If so, if you cut that back then your tank may be able to repair itself which is always the easy answer. For example, I was in a similar situation as you last year (after recovering from the NO3 dosing lol), with no nutrients. I was also using Aquaforest (currently for over a year now). I stopped using Pro BioS/NP Pro, removed the Siporax from the sump, and started removing the skimmer cup at night (left skimmer running). That's all it took to get some nutrients in my tank, well that and feeding the fish 5x per day.
Keep us updated!
Yes, that is correct, I stopped bacteria/NP Pro back in November. Removed the Marine Pure block a few weeks ago. I will continue feeding heavily which makes me happy as my fish are doing great. Will keep posting my readings and observations as Im sure there will be some tweaking to the current plan.
Thanks!