Connections - if it's all on one booking (and BA are prepared to book it for you) and the flight 4 hours later isn't likely to be full (what day of the week are you travelling?), you could always risk the 1 hour connection on the grounds that if you don't make it, it's BA's problem not yours, and they'll have to put you on the later flight.

But
- the later flight may be full and as an MFU I doubt whether you'll have much priority on the waitlist - is the later one the last one of the day?
- your luggage might end up on a different flight from you, although if you're going home that might not be so much of a problem.

Personally I'd take the longer connection and spend some time relaxing in the lounges at LHR.

MFU open jaw - I don't know, can't see why not, suggest you try a dummy booking on the website.