brick wall in tactics training

I hit a brick wall in my tactics training and feel I'm running into the same situation over and over without improving.  I'll have a problem leaving me with two candidate moves that are non-forcing.  I'm overwhelmed by the calculation possibilities of both. Only one move is correct, but both have problems that I can't solve.  If I pick the right move, the computer's continuation is a non-human move that makes the rest of the problem easy.  It will never play the continuation that is giving me problems. 

On the problem 1. Ke1  g3,   is the easy part.

Now my candidate moves are 2. Rxf3  or   2. h8=Q.  

The problem I have with 2. h8=Q is g2.   so white can no longer give black a free move, so I have to check.  There are Rd8 or Qh7.  I spent 15 min trying to make Qh7 work ( it doesn't)  because Rd8 is a Rook sacrifice and I didn't spend a lot of time on it ( although this is right move, but I don't know that).  I don't even know if this is the right 2nd move to begin with.  After all this time trying to solve my 2. ... g2 problem I started looking at 2. Rxf3   Nxf3+.  I figured after Kf1 there is no other check black can give and I can queen next, but I'm just hoping.  Too many possible next moves for black for me to calculate.  Too bad 2. Rxf3 is a mate in 7, but I can see that far. 

So I finally make a guess, If I guess right the line that gets played isn't the continuation that gave me issues anyway.    This problem has a 52% success rating.  There has to be a way to break this problem down so I don't spend 15min going down a rabbit hole trying to make the wrong 2nd move work.   But because it a non-forcing move the branches overwhelm me.  So what do I do to improve?   I didn't see mate in 7 with one move, and the correct move was so unclear.

where does it show a % success rate? ( I have lots of questions on iChess tactics scoring)