I am not sure how i can help you.

All i did was flashing cm12.1 according to RealJohnGalts description and have no keyboard or screen issues.
But i do not have multiboot in use. TWRP is installed but i have flashed to internal.

But i fear your "customer" will not be satisfied as of yet with cm12.1 even if it runs properly. There is no audio, bluetooth and gps in sfdroid for now.

For usabillity reasons you should better try cm11.1 base again and rule out errors.
It is possible to get cm11 running without screen or key issues also, i had it but can not tell how.

Better ask someone who is more experienced with ports than me
I hope you succeed!