Crox, I told you when I first tested your water that there is no way of knowing how long it will take for levels to drop since every tank and everyones individual husbandry is different.
Rather than running tons of phosban, try to find the source of the problem. Also, I've seen a lot of guys running 2 part and adding kalk in their top off water. Most of them run PO4 reactors, yet still have high PO4 and they can't figure out why. Phosban sucks up much more than phosphate. Alkalinity being one of them. I have no proof, but something common with those who dose 2 part and Kalk tend to have PO4 issues. I think it's that too much alkalinity is saturating the Phosban prematurely making it ineffective, yet people will still try to go 6 months without changing it.
Don't dose too much alkalinity supplements while you are trying to get PO4 under control.
Since Kalk has the ability to precipitate PO4, consider using that rather than the alkalinity part of 2 part solutions for a little while.
What's the point of over doing alkalinity supplements for growth when your PO4 inhibits it?