OK then.
1. There isn't too much else info you really need about them. I did, however, change Plot so know he's got split personality disorder in which he's sometimes angry as all hell and sometimes harmful, and one here he's extremely calm and a bit over protective. Also, Jam is a bit of a femboy, and he is also extremely shy. Like, shyer than Fluttershy. Both, as I said, have British accents. Plot's is more elegant and Jam's is more comical-ish. If you can't do British accents, that's fine. Just try the first accents you can think for them.
2. Well, Plot Line didn't accept the relationship at first, and kind of gave Jam a black eye and a broken hoof (which he immediately regretted) , but later agreed when really desperate for Hearts and Hooves Day
3. There's one thing: don't cheat and use Tubby Wubby Pony Waifu, though, I am pretty sure that's not what you're thinking of.