Unfortunately, there's just no way to predict where your weight is going to come off.
That being said you can certainly help the appearance off your arms even if you can't change the size of them.
I have big arms too. Right now they measure at 14" although they can get up to 15" after heavy lifting while they're retaining water, on a good day they
might get down to 13.5". I used to hate my arms but since I've started heavy lifting even though they still won't fit into all the shirts I'd love to wear, when I flex them I have muscle plus they look so much more shapely than where I was before. I'd even happily wear sleeveless shirts (just don't own any at the moment due to $$) because I feel that with the definition they look way better than without.
Part of it too is finding clothes that go well with your arms. I personally like either 3/4 length shirts or sleeveless (I prefer ones that are somewhat gathered at the shoulders, now square ones because then they cover up my shoulders, which are one of my better features). Cap sleeves are just about the worse.
As for weight loss, well, that's for you to decide. At your height/weight you probably don't
need to lose weight to be healthy. However, exercise is ALWAYS good and heavy lifting can certainly help reshape your body. I won't guarantee that you won't lose your boobs, because I really don't know how your body will lose BUT I will say that a well-fitting bra will do wonders.