Sorry all I haven’t reported back.
So, status right now is that we sped up the graphic a lot by a much needed rewriting of the code outside of the DMA-structures and our project managed decided that the speed increase was good enough and told me to put DMAs on the back burner until later.
Only that another project showed up that looked juicier and I decided it was time for a change, so that “later” won’t happen. At least not for me. I will, however, pass on this thread with the recommendations to my colleagues in case that “later” actually happens.
So, at least now you know and this isn’t one of those threads that just stops with an annoying cliffhanger. 
Thanks for the help. I at least managed to get a lot further even though I didn’t manage to get it to work perfectly.