Non-committal and thematic, this move is fine.

8. Rb1 is a good move but so much for preparing o get the bishop out but rather because it protects the b pawn, gets the rook off of the dangerous diagonal and prepares queenside expansion with a3 and b4. Alternatively you can transpose into the kings indian fianchetto variation with 8. d4

d4, please!

8...Bf5 was definitely worth a look. If White responds with 9.e4, the bishop can drop back to d7; if 9.d3 Ne5 (10.e4 Bd7). White is set up for a K-side attack, but Black has a firm grip in the central dark squares,

This move limits the scope of your dark square bishop. You should play on the queenside or in the center.

Rather an unusual move-order, but the thing looks OK to me, more or less. Maybe 9.e4 would have discouraged Black's next move...

how about 10. cxd5 pxp 11. d4 (if Nxp simplest is 12. NxN pxN; more complicated is 12.e4 Ne7 13. Be3 where black plays against the white center)

why is white worried about Ng4? it is not threatened immediately; white's queen could just take the knight if the knight goes to g4. Also to play the knight to that square at some point in the future black would have to weaken his kingside with either h5 or ..Nd7...f6..e5..exchange pawns ..Nf6 and the Ng4 the latter being quite a lengthy mauever during which time the white forces could accomplish quite a bit. That said h3 is not such a bad move. I don't like the position of your dark square bishop. You could follow up h3 with g4 and f5 and although after the exchange of pawns on f5 you have weak pawns on d4 and f5 your bishop has a promising future on either g5 or f4. Further more you have an open g file to put a rook on at some point in the future.

As black I would have played 14..Nd5 threating the bishop while if white plays NxN pxN protects blacks extra pawn and opens up the c8-h3 diagonal for blacks white square bishop.

Nd5 is still good for black here

Black is beginning a Q-side pawn roller, and it's very difficult to find a good defence. 15.a4 is met by 15...b5 anyway, and if 15.b3 Nd5 looks pretty handy.

The Ne4 idea may be better...but first play 17. BxB RxB 18. Ne4 and now if NxN QxN you get a tempo since blacks rook is hanging and if 18... b4? you have 19. NxN+ BxN(or QxN) and you get your pawn back with Qxc4, although here maybe black better since his bishop is better placed.

17.Bxb7 Rxb7 18.Ne4 Nxe4 19.Qxe4 Qd5! and Black has a fine game, by the look. Without the preliminary bishop exchanges, a wholesale set of exchanges on e4 leads to much the same position. But after the text move, Black can establish an advanced protected passed pawn.

Very nice combination. Not only does white restore material equality but the position of whites knight(once it goes to a5 and then c5) more than compensates for the bad position of whites dark square bishop.

Black was too hasty. 17...Bxg2 18.Qxg2 b4 and 19.Na4 c3 20.Nc5 (there's no pawn-fork on c2); or 19.Ne4 Nxe4 20.Qxe4 Qd5.

White probably gets a big advantage after 19..Nd7 d5! finally activating the bishop allowing Nb6 if so desired. Also the opening of the d file puts pressure on blacks queen.

and sacrifice the exchange?

Good prophylactic move. White has a fine game here. The hanging pawn couple is a bit of a weakness, but their dynamic potential goes a long way to disguise the fact.

Why in such a hurry to trade queens? Maybe since you were low on time. I would be looking for a way to play d5 activating the bishop. Maybe transfer the queen to d2 and the b1 rook to c1