for all you know some of these girls might have been too timid or subtle to let on that they're ok with this going further
In my opinion I value a clear "eww" or a  confrontation over having to guess whats going on
 
now I know there's a fine line here, you're with a girl alone, and one should be responsible, I don't want to advise you to push the girl to do anything
this to me is not enough, you think this or that, I'm not saying this is nonsense, its actually very plausible and its comprehensive and thoughtful but,
you do not know what the women is thinking or feeling, she could have all sort of stuff going on even if she seems disinterested and that is from your personal perspective alone
if she doesn't let you know clearly that she doesn't like it or want things to go further you have no idea
im gonna be honest, to me a women not reacting to you putting your arm around her is the opposite of rejection
and her not reacting might just be the sexual tension at work
if a women doesnt like you or isn't attracted to you she's not going to let you put your arm around her for very long, she will throw that arm away or immeditiately confront you, thats in my personal  experience, so to me her not reacting is a big sign that she is ok with it, its subtle
 
now maybe you are used to women giving you clear positive reactions the moment you touch them I do not know
Ive been with women whom I started touching (arm on back or on leg) and they acted for 20min as if nothing was happening, nada, no reaction no comment, and still it turned out they were ok with it and they wanted more
women can be very subtle in my opinion
go in for the kiss or keep touching her, worst case or should I say best case you get a clear rejection, and me I value a clear rejection, it means I communicated my feelings and I got clear feedback from a real person, a real women, not my mind and its mental projections and beliefs
 
on the other hand if you value finding a women with whom you feel clearly from the beginning that she reacts positively to your touch, you're free to do so! each their own desires and dreams