English used in EastEnders (BBC) 1 Sept

[Runs1215]

Hi there, I caught these sentences from 1-Sept Eastenders, but i don't seem to understand them thoroughly.. it would be very great if someone can help me understand the meaning of these lines. Thanks.

1. Crashing down
Reality'll come crashing down and you'll feel you're drowning.

2. Taped off
The police have got the place taped off.

3. Stuck at
All I know is I'm stuck at Dot's with her treating me like a teenager.

4. Him being murdered and you hidding in the bathroom.
a) Why use 'Him being murdered' instead of 'He was being murdered'? is it common to start a sentence with 'HIM'?
b) why there is no verb like 'is, was, are, were' there in the sentence?

Thanks in advance!

[Mister Micawber]

.
1-- Reality will suddenly and roughly appear to you.
2-- A plastic tape is tied around the perimeter of a crime scene to discourage trespassers.
3-- Unable to move/leave from
4a-- Not common, but occasional. The possessive 'his' is falling out of use, though many grammarians still insist upon it.
4b-- It is not a sentence; it is just a noun phrase.
.
_________________
Native English teacher at Mister Micawber's