Digital BW, The Print

Please help me. I am a cheapskate.

My 4oz bottles in my CIS/1160 are running short of the original Piezo inks.
I actually got through this set without the greenies!

Can I just add MIS FS inks into the bottles and continue to print?

Can I add Generations black and mix it with the MIS FS greys?

Do I need to buy a new set of CIS carts?

And finally, I'm really interested in the deepest blacks I can get within
reasonable cost.  I'm not selling the prints so I can live with some future
fading I guess.

I'm now printing on EEM paper but would be happy to print on glossy if there
is a compatible B&W ink to do so. Dye inks that fade in 6 months would not
be acceptable though.

So, fellow tightwads, I welcome your suggestions.

Thanks.
 
-Bruce