Heather wants out plain and simple, from day one she decided she didn't want him and will be cold and stand offing and purposefully try to start a fight just to give a reason for it to end. It's going to be a repeat of Ashley, the perfect person who no one is good enough for. This will play out in just a lot of cringe worthy moments and in the end she'll take no onus for the relationship not working.
Sonia and Nick I think will work, she is emotional but not abusive ala Sam from last season. Nick is reserved but open and shows he cares, they are being awkward but its a natural awkward given the situation they are in. I think once they settle in and have time they will grow, may have a few fights but I am pulling for them.
Tom is going to be a total d**k, if someone refuses to live on a bus in the exact manner of lifestyle you want is a deal breaker - don't go on a show like this or expect someone to conform without willing to have a little give - this relationship will go down in glorious reality tv flames