My fiancé got an email from embassy asking for him to come for reoath, fingerprints, and do a new medical. Is it a good sign? Does it mean his AP is cleared?
Ap - 2.2 years
He lives in Pakistan
Applied for USA visa K1
It's just as easy/hard to deny a fiance/fiancee as it is a spouse, actually. Both visas effectively have to show the same thing, except a spouse has an MC and a fiance has a letter of intent. The main difference is a denied spousal visa due to not having a bona fide marriage can be reaffirmed, whereas a K-1 dies.
That said, this visa application does not appear to have been denied due to the relationship validity. If that was the case, they would refused the visa and sent the petition back by now. I've seen a lot claims against Islamabad, but lack of willingness to just refuse a visa is not really up there.
Extended AP is not uncommon with Pakistan, especially when a DS-5535 is requested (as appears to be the case here based on the OP's statement). Most often this is due to background checks, and applies equally whether it's a spouse, fiance/fiancee, or other relationship (because it's not about the relationship).
Doing an I-130 now (meaning to marry first) would effectively just restart the process. They would have the > 1 year wait for the interview & may (probably) just end up in the same AP again.
Note that they interviewed on 9/24/2018. So it's "only" been slightly over 1.5 years, not 3 years, that they have been in AP. The time prior to AP is relatively the same (give or take months) for everyone from that consulate, so it's not really fair to include that in the waiting period.
While ~1.5 years of AP is quite a bit (even for Pakistan), it's also not unheard of either. I think the most I saw was a little over 3 years of wait in AP.
As for what can be done, the main thing is to keep in touch with the consulate . You can contact a congressional rep to inquire on your behalf, but they cannot influence the decision - only get information.
As a last resort, a Writ of Mandamus (WoM) can be discussed with a competent immigration attorney. I only say discussed as if the issue is background checks, a WoM cannot speed that up. It's only included for informational purposes, not a suggestion to pursue.