On this specific part... I think personally its ok to ask a few questions even if you don't intend to book right now. Obviously don't promise you'll do it tough and keep short and simple. Especially on services, of course if its clearly said "restrictions : this and that" and they still ask i agree its pushing boundaries but if its not mentioned at all i think its fair game to ask no? Not all providers who allow cim or cof for instance will list it on their website. Asking then become the only way to know for sure.They promise to book and ask questions & never book, or they ask for services that aren't advertised and they are just trying to see if I'm willing to cross my own boundaries.
Otherwise im with you on the rest, i know there is lots of time wasters unfortunately.