Endgrain floor on infloor heated plywood w/ crawlspace

I'd like to do an end grain floor. I have a lot of dry slab remnants. Some up to 30"× 2". I'd like to cutting it all around 3/4" and glue down to finish.
Questions- concerned about longer pieces moving too much. I have made a lot of pieces already, I'd like to do sequencing,  book matches for appeal.
What is the best glue? Affordable would be nice. Is titebond III good? Polyurethane glue?
Spacing for movement? Grout (sawdust and Polyurethane?)
Finish,  again,  affordable would be nice.
Species variation. Nothing too soft,  I have a lot of ponderosa,  some poplar.
Bad idea to mix woods?
Other species- apple, ash, aspen, birch, black walnut, box eldervarious elms, honey locust, juniper, silver maple, poplar, cedar-elm, and red/white oak.
I'd love to do some patterns, designs.
I know that is a lot of questions,  but any answers may help.
I'm I Colorado at about 7300' fairly dry climate.
Thank!

Titebond III is good for damp or wet locations... something that should never occur in an interior finished floor. Titebond II is excellent and should work fine for the long term in your application. It has held up for decades in some exterior structures I have built. I can't speak about other glues in this application.

If you are cutting all the pieces into 3/4" end grain sections, I can't see expansion and contraction being a serious issue - the wide pieces will just crack internally if they need to shrink a lot. There will be lots of closely spaced joints, so no place for stresses to build up without relief points. Let them all acclimate to the space before gluing, as for any flooring. I presume you will be gluing the pieces to plywood subfloor; wood planking would definitely have movement issues.  

Thanks. It is getting glued to plywood subfloor.