"I need a new set of dinner clothes and I've decided to bespeak one. What do I need to ask to ensure that I'm getting true bespoke and not "custom" or made to measure?"
I suggest you focus on the tailor's reputation and whether you like the work rather than the technical details. MTM with a hand sewn collar and shoulders is often a better product than the machine sewn bespoke I see coming out of some small tailor shops in the United States.
"Is there a specific type of brush you recommend for suit care?"
In my opinion, the double sided Kent CC20 is the most useful brush for suits. £29.50 (about $60) directly from the maker.