well, don't i feel foolish. i ended up pulling the spotlight down from the bulb and got the effect that i wanted more or less, still with some tweaking to do:
i guess i hadn't pulled the light far enough out of the bulb previously. not sure why it wasn't just coming through the bulb glass from the interior, i suppose there was too much reflection inside? i turned up the subdivs and samples on the irmap, thomthom - that helped with the shadowy artifacts - thank you!
below is what i mentioned regarding the blotches from the emissive bulb material. i had it turned up to at least 100 intensity to achieve a decent amount of light - but that was probably way too high. with irmap quality improved the blotches of light are less intense than before, but you get the gist from this render:
thanks!