It's hard to say. For one he was pretty bored on his own while Star was off at a party, his parents weren't home either or sleeping.
Then there's the painting telling him it's Blood Moon tonight, 'the moon of lovers'.
When they returned, he had this 'I told you so' attitude. Like going along with an agressive demon ex is a bad idea and 'I told you it was going to go to bad places'. You could make the argument here that he was just looking out for his bestie's safety. 'Never go with a predator to a second location' and all that.
But as I think and as Star has pointed out, he didn't NEED to go to the ball. It's likely that nothing bad would've really happened if he didn't show up and steal the dance Tom was probably preparing for a really long time. And if things would've went sour Star has demonstrated that she can disable Tom as a threat in an instance. (ice works really well against demons who would've thought?)
And the last thing to consider is his face after Star tells him that 'I don't need a hero, I need a friend.' He look pretty crushed here, doesn't he?
Was it because he genuinely had romatnic feelings being developed for her and was shut down OR was it because he didn't trust his bestie to deal with things on her own (a pet peeve of Star is people underestimating her) and dissappointed her. Which as her bestie he would never want to do.
Things are not exactly clear cut.