Recent Sicilian Blunders

I recently played an interesting sicilian game here on chess.com with the white pieces filled with fun tactics and some blunders thrown in the mix on both sides.  It was a loss but I learned a lot from postmortem analysis.

The first moves were 7 moves were uneventful:

Here is a diagram of position:

At this point I have the initiative and could refute blacks last move by playing Be3!!!  This poses the threat of Nxc6!  where the queen would be attacked by the masked bishop and overprotects my knight on d4.  The threat is easy to parry by removing the queen from the g1 - a8 diagonal and is pretty much forced to move to c7 in order to not lose a pawn.  Unfortunately I didn't play this in the game but instead resorted to the inferior move Qd2.  My idea behind this move was to either castle on the queenside or at least bring a rook to bear on the semi-open d file.   

My opponent followed up by playing Bd7 to release the pin on his c6 knight.  My knight on d4 is in danger of being won so I withdrew it and played Nf3.  At this point I conceded the initiative to my opponent and some interesting tactics came up next.  

Here are the next few moves:

The Nxd4 move took me a little by surprise in terms of its execution.  I saw it ahead of time during the game but didn't think my opponent would play it on account of their week d pawn.  With my 13th move I was trying to regain the initiative by putting more pressure on the open d file.  I also thought that black was in trouble when they castled on the queenside.  

The game continued:

I definitely overlooked the consequences of my opponents "quiet" 14th move, e5.  In retrospect it opened up the diagonal for their bishop to become active and put me on the defensive due to the discovered attack on my queen.  I thought that played Qa3 in response would win the pawn on a7.  My opponent didn't do anything to defend it and they were playing a great game so I thought it might be some kind of trap and therefore I didn't take it until much later in the game.  If I took it right away with my bishop I thought it might get trapped with b6.  Here is the dilemma in all its glory:

My next mistake / inaccuracy came on the 18th move when I moved my rook over to e1.  To be honest, I didn't know what to do so I tried to play a prophylactic move here.  I thought my opponent was going to play Be4 to pin the unprotected knight.  The next move by black seemed to come out of the sky and totally floored me.   It posed many threats and every way out looked like a disaster to me.  I played the pathetic Qb3 in order to trade off queens and hopefully get a chance at a draw.  If I played c3 instead I was thinking black would lift his rook over to d3 and then bring his other rook over to the d file to mop up.  After this point in the game it felt very unpleasant to play the white pieces.  Eventually I ended up resigning due to the undisputed loss of a minor piece as you can see by the final position:

How can I prevent Rc8! followed by b6?!?