You're doing very well and are to be commended for your commitment.
I'd say you should be close as well. My nitrites were high for almost 3 weeks before they came down. A pwc is a good idea at this point; it may take more than one to get the nitrites at a readable level (<2 would be best). Then as you said, dose ammonia to 1 for a few days to let the bacteria catch up then go back to the 4-5 dosing. Nitrites might rise again. If they do, another pwc shouldn't be needed unless they stay high for over a week with no sign of coming down.
As for the nitrate, are you using the API kit? That test is very easy to get incorrect results with if the test isn't done exact. I'd shake both bottles well before using them (particularly bottle #2 for the full 30 seconds the test kit says to shake it for) and bang the bottom of the bottles on a table. Bottle #2 has a reagent powder that tends to get clumped and can cause incorrect readings. Also be sure you vigorously shake the test tube for the full 60 seconds. You should be seeing nitrates by now but it's possible the high nitrites stalled some of the process. The water changes should help. Let us know what happens.