What is the highest version of Android I can get on my Droid X?

Im a developer and really need something to test cordova apps with. According to their site they support 2.3 as well as 4.x and higher.

I have a DroidX and have spent a good amount of time the past few days trying to get it to something 4 or higher (due to 2.3 not working for my testing)

Maybe Im misunderstanding something but I thought that CM [cyanogenmod] would get me to Android 4.x so thats what i have been trying to load?!

but everytime I sbf down to 2.3.340 I get an error in bootloader (trying to do this to use CM ):
30,04 - Err:A5,70,70,00,1F - NEW_MEM BLANK

I can successfully get to 4.5.604 (and remove the error above) but than CM complains when trying to install it:
"assert failed: run_program("/tmp/check_kernel") == 0"

I can load Apex 2.0.0 RC4 (or other compatible [for .604] mods) but these seems to be Android 2.3

So
What is the highest version of Android I can get on my Droid X?
if CM is the answer, what am I doing wrong on the install? Why does it need 2.3.340, I thought only the hack for root access needed that version, not the mod itself?