Firstly, if you feel your a/c was endangered by the proximity of another, an Airprox Report should be filed. The Jetstream crew may have have already done so. You're obviously intent on learning from the experience (fantastic!
) so give others a chance too!
Secondly, even if you've spotted the traffic don't assume he's spotted you. You may be snugly hidden behind his window frame. Thus also don't assume he's going to manoeuvre lear of you.
Thirdly, be careful about fixating on reported height unless you are certain of which pressure setting you're both on.
In general, it's prudent to keep an extra-special lookout around IFR let-down areas. The a/c flying the procedures will of course be that much more "heads down" following their instruments.
Anyway, good on ya for talking about it!
ap