I added to the miniroot 14.1 the whole package series "l, x" and added a few packages here and there to get X working (fluxbox, utmpter, nettle, libtiff, mpfr). Linked xinitrc.fluxbox to xinitrc and fired up startx without even configuring it.
I then ran xorgsetup just to make sure it was working and for me it ran OK.
I had a look at the difference from your bust Xorg lo9g and my working one. This is the first thing that struck me:
[ 5744.121] X Protocol Version 11, Revision 0
[ 5744.128] Build Operating System: Slackware 14.1 Slackware Linux Project
[ 5744.134] Current Operating System: Linux slackware 3.10.29 #1 PREEMPT Thu Fe
b 13 22:01:13 GMT 2014 armv6l
[ 529.313] X Protocol Version 11, Revision 0
[ 529.314] Build Operating System: Slackware 14.1 Slackware Linux Project
[ 529.316] Current Operating System: Linux armslack 3.12.26+ #704 PREEMPT Wed
Aug 20 22:35:11 BST 2014 armv6l
Could it be that FB support in yiur kernel has something wrong ?
# zgrep _FB /proc/config.gz | grep -v "^#"
In any case here's mu whole Xorg log: