I lost a long write-up for this move when I accidentally closed the browser window (if I'm going to write essays, I should do so in notepad), but here are the main lines:
I'm having a difficult time seeing how to increase Black's advantage here. The main possibilities that I see are the two I mentioned above: Ra7 and Qb5.
16...Qb5 17.Qc6 Bc7* 18.Qxb5 axb5 and Black might be able to make trouble after 19.Rc6 with b4-b3 and b5-b4. This seems OK, but is pretty committal.
After 18...axb5
*17...Qxe2 doesn't seem to work, and after 18.Qxd6 N7f6 looks to lead more or less by force to
Variation, after 22...Rxb2
which seems pretty much drawn, once that rook on b2 gets chased/traded. The motivation for looking at this is that Rfc1 weakens f2 and the threat of Nd7-f6-e4 to support that attack (while the queen hits b2) might be something. White just plays Bxf6 to kill it, which is what leads to the above result. (White's queen takes on b4 and then returns to e1, where it is exchanged.)
So we return to the main idea, which is 16...Ra7. White has 17.Qb3 which is a little annoying, but after Qb5 (hitting the knight, with the idea Rc7) Black should be able to get the c-file back (if White protects with Rc2) or exchange queens (if White protects with Qc4). But 17.Qc6 seems critical, and Qc7 18.Qa4 (avoiding the queen trade seems best, and this is a good square for the queen, which I had hoped to prevent her from reaching) Qb8 Black will, at least, be able to contest the c-file.
After 18...Qb8
I'll console myself by noting that if Black had opted for 14...Qb6 instead, then we might have reached
Variation with 14...Qb6, after 17...Qb8 so the queen dancing was worth something.
**
I think my longer-term thinking here is to trade all of the major pieces and try to make something happen in the minor piece endgame. I'm not sure that's the best plan, but it's the best one I can come up with...
**
Comparing the first and third diagrams, I'd rather have the third, even though those doubled pawns are covering some nice squares, not being to contest the c-file easily makes me a little nervous.