The fact that BL stole over $1,000 from Gabby during his run from Wyoming to Florida makes me believe he was trying to form a plan of escape or evasion. He had no need of that much money for gas or transportation just to get home to Florida. It sounds to me as though he was planning on surviving the best he could and he knew he would need money to do that.
So, I think that at the time he took the money, he was not thinking of suicide. He very well may have reconsidered his position once the repercussions of his actions became reality with all of the parents' efforts at contact and then LE started knocking at the door. But during his run home, I don't think that was his intent.
I do pause here, though, because we really have no idea if he withdrew money with her credit card account(s) or if he actually charged items against it, do we? But in either case, it indicates to me that he was trying to form some plan at survival at this point ~ typical of the 'survivalist' image he had of himself. Still slowly MOOing along.