Hello and Welcome to Armaholic!!
I have a few questions for your first.
1. Did you use the modfolder method to install SLX?
2. Have you tried playing the missions without SLX to make sure its the problem?
In regards to the CTD of SLX, its a common problem with the mod. Solus (the author) did a great job with executing many good ideas but there are many errors, problems with new patches, script lags, and problems with a few of the PBO files. Unfortunately, he has disappeared from the community and the mod has been halted. Gunter_Severloh however has made a "bug list" of SLX you should take a look at here
. I would also recommend removing any pbos that are not necessary as the large amounts of scripts can bog down the game.
I do not use ACE so I don't know if you should try it.