The 14 is a very weight-sensitive boat, as you've discovered the hard way. Unless you aand your crew weigh <100 lbs, then it's a singlehanded boat.
310 lbs of crew is just too much. That's a full crew weight for a 16.
The jib blocks are attached via a wire that runs underneath the trampoline, from chainplate to chainplate. There should be two large grommets in the tramp, right over the wire. The jib blocks attach to the wire with a shackle through the tramp grommet.
I'm not sure what's snagging on the mast - are the sheets getting caught in the halyard cleat?
Until you're confident tacking the boat with the jib, I wouldn't take it off yet. The 14 is probably the hardest boat to tack without one.
No wire came with the boat, apparently the prior owner was using a piece of line as I mentioned. Is that the Jib Block support wire? I'll try to find a place to purchase it.
Regarding the mast snagging, there are a couple of things going on. First there is a cleat on the front of the mast that shouldn't be there but I know the solution to that issue. Secondly the sail gust seems to be getting caught as it's coming across.
As far as taking of the jib, there is always jibing as an alternative. I'll try giving the boat another go soon. For the moment I'm also breaking in the 16.