Dogs of different sizes

Question
Hi,
I have two questions.  I have a 7 month old, 50 pound lab mix that I got from the shelter when she was about 7 weeks.  I also have an 11 month old, 12 pound pomeranian mix that I was given by my neighbors three months ago.  The lab mix is very playful, and wants to play constantly.  The pomeranian mix also likes to play, however the lab mix is fairly rough with the smaller dog.  She grabs at her neck, legs and back, and will often tackle her.  The pomeranian mix will usually put the larger dog in her place when she is too rough, but the smaller dog also entices the larger one to chase her and will often bark at her to play if the lab isn't playing with her.  I'm afraid the lab will hurt the smaller dog, and am not sure how to teach her to play more gently.
My second question deals just with the pomeranian mix.  She was 8 months when we got her and had been an outdoor dog for at least three months before that. I've had her about 14 weeks, and have had a great deal of difficulty house breaking her.  She is in a crate while I'm at work and a petsitter comes midday to let both dogs out to play and do their business.  She ususally holds it while in her crate, but will sometimes urinate in her crate.  She will also sometimes urinate out of excitement or urinate submissivly, however, these two issues seem to be under control.  The lab is already housebroken, and I'm afraid that 1) I'll never get the smaller dog house broken, and 2) that her indoor accidents will cause problems with the lab.  I'm not a "small dog person" and was planning to train the pomeranian and find it a good home, however, now my boyfriend is insiting on keeping her, and I'm finding the housebreaking issue to be very stressful.  Any advice you can give would be appreciated.
Thank you.

Answer
The mid day break with the pet sitter is a good idea.  I am constantly telling people they should do that.  Is the problem mostly in the crate?  It won't solve the problem, but make it easier to cope with if you put a grid in the crate to keep it up out of the urine.  They are available with the crates, but expensive and hard to find. A piece of closely spaced wire closet shelving from a home supply place is cheaper. I am now using a plastic vegetable bin with plenty of holes drilled in the bottom.  Here is a link to a picture of my Holly in it, http://www.photolocker.net/images/Labman/hollyhighanddry.jpg

Many dogs eventually outgrow it, but you can reduce it by building the dog's confidence up.  Start with obedience training.  The key to most behavior problems is approaching things using the dog's natural instincts.  Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog.  Life is much easier if the 2 legged pack members outrank the 4 legged ones.  You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/  As you praise the dog for following your commands, it will build its confidence.  

Play tug of war with the dog and lose.  However at the end of the game, take the rope or toy and put it up, less the dog becomes confused about who is top dog.
Ropes from the pets' store quickly turn to hazardous shreds.   Ones I made
lasted much better.   Go to a hardware or home center that sells rope by the
foot.  Buy 2' of 3/4" poly rope.   Melt the ends, and tie  knots in it.   Get
them as tight as possible, put it in a vise and pound it with a hammer.  Watch
carefully, and be ready to discard when it comes apart.