Mindy, thanks for so much information. I do hope the doctors can find something to make you feel more comfortable.
Before I forget half of what I just read, let me address the issue of toys and tummies.
Rawhides are bad, bad, bad as bits can come off and cause intestinal blockage. That is the last thing Ruby needs. I discovered with my sweet little Oliver that a toy has yet to be invented that he is unable to destroy. Forget about giving Ruby soft toys as they will end up being destroyed and again, pose a danger to her.
A kong, filled with the food she normally eats (and consider the food you put in it as part of her diet) can be fun. Normally I would suggest putting some peanut butter in it, but since she has such a sensitive tummy right now, I don't think that's a good idea. (You can do that later when her tummy is less sensitive as too much peanut butter gives my boys diarrhea.) However, as with any toy, she must be watched at all times. It will keep her busy for a wee bit.
Another very useful thing is a plain, old face cloth. Dampen it, and twist it, and freeze it while twisted. It will not only soothe her gums, but will provide her with a chew toy that is not harmful and is reuseable.
I'm glad to hear that she is gaining weight. I know only too well how much damage can be done to their wee tummies when they've had a parasite as I went through this with Henry when he had Giardia. Time is your friend and as your Vet pointed out, as she grows, her tummy will have a chance to heal and become more resilient to these things. It just takes a while.
As much as I hate to say this, you may wish to find an alternative to a Christmas tree this year. It sounds like you aren't feeling the best and unless you can cordon off your tree completely from Ruby, then you will constantly be jumping up to stop her going for it. In the past, I have used large potted plants and put lights on them, and put them on a table. I left all decorations in the box. It just saved a whole lot of headaches and even the children understood.
Santa was still able to make it down the chimney to fill the stockings even though the boys were older by then.
It sounds like the cats and Ruby are finding their way together. I'm sure you are very excited about your sons impending visit! I'm sure he'll understand if there is no tree.
Happy (belated) Thanksgiving to you Mindy. We already had ours here in Canada back in October but I've been enjoying celebrating the good wishes with all of my American friends.
Best wishes to you, and hugs too.