It seems as if you are not pack leader!! Rotties are just to big and confident to have a wishy washy handler! Try to do the following things!
You need to become the giver of all good things! No Free Lunch. Make Harley work for every morsel of attention, food, toys, walks ect. Make sure YOU give them to him! By doing this you are establishing your dominance. You are doling out the resources. Make Harley sit for a treat, down and stay for breakfast, sit at the door while you go out first and then he goes ect. As boss you go first, Harley follows!
As for the pulling try walking Harley 10 paces forward. The moment he starts to pull automatically change direction. Keep doing this but change the number of steps and the area you are practicing! Dogs quickly recognize patterns so be on top of changing the pattern. You will begin to notice Harley hanging back more and more. He will begin to look to you for direction.
When you feel confident that his pulling is on the mend start adding in distractions. Work him close to your neighbors beagle. So close that he realizes the dog is there but far enough that it isn't a big deal. If he pulls increase the distance between the 2 dogs. As he gets better with the dog start in closer. The moment he pulls increase that distance again. Try this with anything Harley has a problem with. This requires intense consistency, but Harley will get it;)
A search of threads under residential training will bring up alot of issues with boarding training. Please read it! There are alot of good points mentioned.
As for your tiny stature.......I've seen tiny 4-H handlers working thier rotts in obedience..... they don't have problems.... your rott may be stronger then you... but don't let him outsmart you
All the best!