Hi there

First posting - urgent issue because I want to get home from work safely tonight! And you'll have to excuse me because I'm pretty ignorant about cars - the Merc is my partner's pet project with the WVO thing.

In brief:
1) Brakes became hard after 40 mins of driving this morning and slow to stop completely.

2) Door locks don't seem to be working too good.

3) Engine wouldn't stop running when I turned the key - could take keys out and it was still going.

4) Got one of my work colleagues to stop engine - he blocked air intake thing for about a minute, then car stopped when it was unblocked

So, checking on postings and other sites, I'm pretty sure we have a vacuum leak problem which my partner thinks he can fix okay, but I still have to get home tonight.

Couple of questions:

1) How safe is it going to be for me to drive it home? I'm a bit worried about the whole hard brake thing, so am intending to leave well before peak hour, give myself extra braking room but it's still a 45 min drive, downhill mostly, to get home with lots of traffic lights.

2) Will it start okay since we "suffocated" the engine to stop it?

3) Does the 1979 300D have the fuel pump safety off switch / lever I've read about and is this a better option than cutting off air to stop the engine if I have to do that again? Just thinking about damage to the engine long-term if I have to do it more than once tonight.

4) Given I know zero about cars, am I on the money with the vacuum leak idea or could it be something else?

Any help hugely appreciated.

Thanks heaps

Ripley