Gravitas

The place to kill off Matt Kowalski was when they were making the unpowered approach to the damaged ISS.

Serves the plot in the same manner as the unexplained acceleration at the end of the tether and doesn't have unexplained acceleration!

Killing him with an impact also would explain why she doesn't even try eliminates her attempting a rescue with the remaining Soyuz.  It's not like he could get too far away by the time she cycled the lock and started pre-flight checks!

Never mind that orbital mechanics just don't work as shown.  The Chinese did blow up one of their satellites and there was a lot of concern about the debris cloud.  And it took hours for the bloom to spread and develop so that the danger could be assessed (Remember: Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.) To this day nearly all off that debris is still pretty much in the same orbit as the satellite started in.  Why?  Because there's been nothing applying any force to the parts once the impactor hits the satellite.  Yes, parts are smashed loose and spread away from the target but the speed of a bullet is not that fast when you're talking about orbital separations.

Then there's the bit that the ISS, Shuttle and Hubble are in very low orbits compared to most satellites.  For something higher to come down and intersect gives it one hell of an elliptic shape.  Elliptic enough to make one pass on one of the three habitats before hitting atmo.

I am not pulling this out of my ass, I am laymanizing from very detailed analyses (which themselves have been dumbed down because CALCULUS and ORBITAL PHYSICS be all full of maths).

I know it's a drama, but dammit; can't there still be drama where the laws of physics are retained.  Once you break physical laws, you may as well dump all pretense at hard science an go with throttle up on the reactionless drive.