Well at 60lbs, her weight sounds fine. Being a girl, she very easily could be under the 80lbs. The rule of thumb is that they gain about 10 lb per month the first year. But it's just a guess and it vaires from month to month. And around 7 to 8 months, they are going through the "puppy uglies" where they are gangly, thin, and goofy looking. Between 9 months to a year, they start to fill out and look like real Newfs.
Still, I would consider cutting her back on the amount of food. Feed her twice a day instead of three times. If you are uncomfortable with 4 cups per day, start with 2.5 cups per meal and gradually drop it back.
Get her weighed just before you start and then weigh her in another month. If she is gaining any weight , then you're OK but if she starts to lose weight, add a small amount back in. Puppies do expend a lot of energy so you have to meet those needs but not to the point of over feeding. Remember that she is genetically programmed to reach a certain size and weight assuming that she get the nutrients she needs. And you want her to grow slowly anyway to protect her joints.
I think that this will help her "output" but as I said, it doesn't cure her housebreaking problems. You still need to work on that. Supervise, supervise, supervise. Don't fret too much about the nightly problems. I think with less food they may go away.
As for anxiety, it's a possibility. Only a person who specializes in this behavior problem can tell you. It's difficult in this kind of forum to assess with any certainty.
If their is a certified behaviorist in your area, consider making an appointment. I think that it would only take one session to determine if this is part of her problem with soiling. Try keeping a journal of her behaviors for a couple of weeks. Just jot down when she does have a problem of some kind like soiling or chewing and see if a pattern develops. Is it only when you're gone, is it in a certain area, what time of day, etc. You probably already know most of this but sometimes it helps to keep notes. And if you do see a professional, you will have something specific to show him or her.
I don't think this is anything that you can't deal with. I know it's a real headache and discouraging but believe me, I've been there and it's do-able. The key is to keep your cool and keep a close eye on her.
One of the things I did initially to help my girl is to stick to a VERY rigid schedule in the beginning. She ate at the same time, went out at the same time (unless she asked to go earlier), went for walks at the same time, etc. and, my routine of coming and going, etc was very rigid too. That meant, no special outings or shopping trips for me for a while. I came and went at the same time every day. Dogs do thrive on routine. You won't have to keep it up forever.
Also, if anxiety is part of her problem, then it's very, very important that you don't make a big deal about leaving or coming home. No fussy goodbyes or hellos. When I come home, my dogs are basically ignored for the first 10 minutes, even if they have soiled their crate or the house or are wildly excited to see me, and then they get some calm attention. If you come home and act distraught (if she's had an accident) then that only adds to her stress. Or if you are too happy, then she will be more anxious when you leave again. While it's nice to have "someone" who is happy to see you, it just adds to the anxiety/stress level. You will have plenty of other opportunities to play and be joyous with her. So, when coming or going, just be very non-chalant. When I leave, I go quietly with out any long goodbyes. I try to not give too much or any attention for about 15 minutes or so before I leave. I do say "bye, bye, be good" and walk out the door. It's the dogs' clue that I am leaving and will be gone for a while. They settle right down and get comfy again knowing that this is part of the routine. Actually, this is a good routine to have even if your dog isn't anxious. It makes everything much less stressful for the dog and you.
Anyhow, good luck and keep trying. Don't give up. She needs your understanding and support and I know you love and want to help her.
