Sounds futile if you live near a field. The rat population is probably high enough that nothing is going to stop their trying to get into the compost pile for whatever goodies may await.

Why not just have an open bin (sounds like you have plenty of space) and let the rats play around? As long as the pile is far from the house I would not think there would be a concern about the rats entering the house.

Might be a rat, more likely a field mouse or squrrel. What tracks lead into the holes? If there are none now whatever made the holes in the compost are not there and pouring ammonia is a waste of time, energy, and money. If there are tracks, indicating use,a trap may be a much better option.
I have never heard of that use of soda but I can think of no better use for soda than that, except it does not work any more than rice, or other expanding grain, or baking soda does to ants.

If you really want to keep them out, which I personally would prefer to do, more for the danger of diseases like leptospirosis, etc., which your dog(s) as well as you can get, then using traps, or sprinkling ground cayenne pepper in front of the holes or dried mint leaves, might work. I know the cayenne will keep squirrels out of my bird feeders - I mix it with the seed in the storage container. And I have been told, and tried in my brother's tackroom (until he got a cat), that essential oil of peppermint mixed with water and sprayed several times a week around the area will keep mice out. The drawback is you have to keep doing it. But, if you are going out to your compost pile several times a week with scraps anyway, then using something each time to keep the beasties away won't be a problem. You can also try using rat traps, if you can think of a bait that won't also attract dogs - I would toss the carcasses off into the field, using washable or disposable gloves - and let their "friends" take care of them. If, that is, your dogs don't also patrol the field, when I would wrap the carcasses in newspaper or a plastic bag and toss them in the garbage.

Up here in PA woods, our problem was with skunks who like grubs and worms in the compost. I line sides and bottom of plastic composter bin with hardware cloth (like chicken wire but smaller holes and very sharp on little claws or teeth). No critters in there now except worms, who get through mesh with no problem.

Same problem here last summer. we start
to water the pin regularly & keep it wet. The water will help the mulch developing & keep the rats or field mice away.

I have heard that mice are repelled by mint. I think it was that wonderful book, 'Carrots Love Tomatoes'. Same would go for rats and other rodents do you think?