Well on your second question I would say yes
You could judge INT if you think she didn't attempt for the ball cause the runner was there. A more clear cut example (not that it would happen but it makes a good point) if F3 was in the base line with R1 on 1st and a line shot came right up 1st baseline and F3 turned her head and saw R1 standing directly between her and the ball and didn't move I could have INT again HTBT to judge if she really stopped cause of R1 or cause she thought she couldn't get the ball, or was just a lazy 1st baseperson
IMO for what that is worth, I think most cases I am going to have to see the fielder attempt for the ball and then pull up because of the runner. I see it as I think of OBS, the runner just being there is NOT int, they actually have to hinder the defense from making the play, and that is where the judgement comes in and where 3/4 of our game checks are earned.
Again I think either can be INT, but you HTBT to see what the hesitation is like, again you have to judge if F6 pulled up because of R1 (then it is INT) or did she think the ss was going to field it, and she needed to be at 3rd for a possible play? Or did she think about it and then realize she had no chance at the ball and making a play on the ball at its location. Again these are judgment calls based on seeing the play unfold. But to answer you original question I think you could have INT in both cases based on what you see in the actual play under consideration, or you could have a no call based on what you saw.