I understand your frustration, but I encourage you to stay with attempting to get it right. The lock miter joint is a great choice and while it can be frustrating, it's worth messing with until you get it right.
I assume that you have the setting right and what you are dealing with is just the feed and as you say the "kick back" issue.
Are you cutting end grain or with the grain. It's the end grain cuts that I have had the most, but not all, of my problems with.
What is the width of the workpieces that you are cutting into if the cuts are end cuts.
If the width is narrow, less that three inches, I have problems and so I try to make the end cuts with wide stock and them rip the work pieces to the correct width after making the cuts.
Let us know more about what is going on in regard to, your set up, is it correct, what is the width of the workpieces if you are doing end cuts. I keep assuming that you don't have problems when cutting with the grain, but that is only an assumption, so let us know know more.
Also, again, my assumption, but need to be sure, do you have your router running at it's lowest speed?
Will wait go hear from you,