No salt would not be a good idea since it is know to cause vomiting if she swallows it.
You need to stick with the dog toothpaste.
Is there a problem with the toothpaste?
1. You can have her teeth cleaned under anesthesia. The vet will have to examine her and do bloodwork to make sure all her internal organs are functionally properly for anesthesia. Then it will be safe.
2. Your vet can prescribe oral antibiotcs. If the infection is severe, and she can not go under anesthesia, you can do what is called "pulse therapy" with the antibiotics. This means the antibiotcs could be given one week on, three weeks off for example. This keeps the bacterial counts down in her mouth.
3. You can use one of the oral rinses on her daily. I am not familiar with the one you mentioned. But here are the ones I use.
I have also been using this water additive on in the water dish of my 3 dogs.