I think you did fine there. It really was not a situation that allowed for you to win much. The only opponent was you had just got a free look from the BB and could have had anything. The call on the turn might have made me suspect that he had a flush or straight draw or possibly just a high card he was trying to catch a
bluff with. Once the river hit and he checked I would be a bit confused. Did the third spade help and he is hoping to check raise (which would have been great for you) did he miss and will dump to anything?
I think your bet on the end was good. I believe he would fold to an all in play. I think he likely hit a small flush on the end that he wasn't comfortable betting if he was behind but couldn't lay down.