Four Juniors And A German (part two)

IN round two of the 69th Hampstead U2200 I got down to a minor-piece ending on move 31.
A long manoeuvring game ensued, eventually reaching the following position:

White to make his 55th move in Spanton (1906/171) - Anum Sheikh (1573/161)

*****
*****
*****
*****
*****
*****
*****
*****
55.Bd7?
White has serious winning chances after 55...a4 56.cxb3 Bxb5 as White's three pawn islands are much easier to defend than Black's four.
55...Bf8?
Black should have diffused the queenside threat with 55...cxb3, although after 56.axb3 White's more homogeneous pawns give him a slight edge.
56.Nc2?
Again the thrust a4 was strong.
56...Nd3?
Unprotecting d5 is a mistake. The best solution was probably still ...cxb3.
57.Bf5?
Correct was 57.Ne3, forcing 57...Nf4, and then 58.a4.
57...Nf4 58.Ne1
Now 57.a4?? is a losing blunder because of the simple 57...cxb3.
58...Kc6 59.Nf3 Bg7 60.Ne5+?
I had run out of ideas by now and went back to my old sin of  trying too hard.
60...Kc7?
Black seems to be winning in all lines after 60...Bxe5 61.dxe5 b4, eg 62.cxb4 axb4 63.bxc4 dxc4 64.Be4+ Kc5 65.Bf5 Ke5, or 62.Kc2 Kc5 63.Bh7 bxc3 64.Kxc3 d4+ 65.Kc2 cxb3+ 66.Kxb3 Kd5 (main analysis by Komodo9 and Stockfish 10).
61.Nd7?!
Both 61.Ng6 and 61.bxc4 look safe enough, but the text is bordering on losing.
61...Ng2
White faces a tricky choice after 61...b4! Best appears to be 62.Nc5! bxc3+ 63.Kxc3 Ne2+ 64.Kd2 Nxd4, when Black has won a pawn, but it seems to me White saves the game by  forcing knights off with 65.Ne6+ Nxe6 66.Bxe6. The engines believe Black has the upper hand after 66...c3+ 67.Kc3 Kd6 68.Bf7 d4, but I can see no way for Black to make progress in this opposite-coloured bishops ending.
62.Nc5 Nf4?!
62...cxb3 was safer. The text allows White one more try.

White has one last try

*****
*****
*****
*****
*****
63.Bd7
The try was 63.a4 bxa4 64.bxc4, but after 64...a3 65.Kc2 Kc6 66.Be6 Kd6 67.Bf7 Ne2 68.Nb3 Black seems to hold with 68...a4. White can try 69.Nc1 but 69...Nxc1 70.Kxc1 dxc4 is a drawn ending of opposite-coloured bishops. That leaves 69.Na1 but it can apparently be met by the spectacular 69...Bxd4!! 70.cxd4 dxc4 71.Bxc4 Nxd4+ 72.Kd3 Nf3 with a position the engines reckon is dead drawn.
63...Kb6 64.Be8 cxb3 65.axb3 b4 66.Na4+ Kc7 67.Bf7 bxc3+ 68.Nxc3 Kc6 69.Ke3 ½–½