Ice maker to sump pump has water run back into it, any ideas for a fix?

The placement of the connection of your ice machine drain is causing the wastewater to drain into your ice machine drain pipe.

• With the faucet fully on, the section of the pipe highlighted in blue is filling with water.
• When pipe is full and even with water flowing through that section, you can see that some water will be entering the ice machine drainpipe.
  

See picture below.

The other issue is that the ice drain should be connected before the P-trap. Attach the ice machine drain to the vertical section from the drain. Making the connection on the vertical section will likely force you to add a condensation pump to the ice machine drain. Many of the condensation pumps have a back-flow prevention valve on the outlet.

It appears to me that your problem is that the ice maker drain is BELOW the trap. So anytime there is water at that level, gravity will draw it into your ice maker drain.

I think you'd be better off locating the in the vertical section of sink drain ABOVE the trap.