does heating xylene increase the solubility of dmt in xylene enough that it would be worth heating the basic solution during pulls as heating naptha greatly increases yields? or should FASA pulls be done at room temp?

Heated solvens (almost?) always have the capacity to hold more spices. Heating might be an important trick when not-so-good solvents for spices are used (aka naphthas) but it is not that necessary for solvents that are good for pulling spice.

Warm xylene will anyway pull more spice that room temperature xylene.