Welcome. Hope we can help.
You'll find that pavement setups are quite different than dirt setups because the surfaces are so different from each other. In your case, if your class rules require what is essentially a factory stock car (and the car you bought has not been extensively modified for pavement racing) then you should be able to convert it fairly easily and cheaply. The biggest changes will probably be ground clearance (higher for dirt, to get more body roll), track width (narrower for dirt, again to get more body roll), and bolt-on weight placements (yet again to induce more body roll in dirt). Why all of the body roll? Because dirt is softer than pavement. On pavement you basically want the tires to get their grip by keeping their treads as flat on the surface as possible (particularly in the turns). But because you can get tires to dig into dirt, you will be trying to get the tire edges (particularly on the right side of the car) more involved. You didn't ask, but I am including this because your scaling for pavement probably is not optimum for dirt.
Note that what you are calling "tow" is called "toe" / "toe-in" / "toe-out" by racing mechanics.
About your questions: 1. Probably. All racing is tough on street car parts, and the bigger tire on one side will exert more force on that side of the transmission. Probably will wear out CV joints quicker on that side. But you do need stagger to make a dirt car handle, so it is a price paid for racing. BTW, keep an eye on your spindles, too - particularly on the right side. They take a lot of abuse while racing, and some crack. Some tracks allow replacing original spindles with beefier spindles - check your rules, and ask some of the large racing parts suppliers.
2. Your rules might limit your tire selection. Because dirt is softer than pavement, you'll want softer tires (not street tires designed for long life). If you are using tires that follow conventional street tire marking conventions, look at the treadwear indicator number on the sidewall. The lower the number, the softer the tread rubber. However, age also affects tire softness (as well as number of heat cycles it has seen, and how it was stored). Better to use a tire durometer so you can measure what you're buying, as also so you can find how your tires are changing as they age. BTW, tire durometers can vary - it is best to stick with just one gauge because although absolute measurements are somewhat important, repeatability is more important. Your tire pressures will be much less on dirt than on pavement.
You can manipulate tire softness via chemicals, and you will find that (typically) the softer / wetter the track is the softer your tires should be. BUT first make sure your rules allow using tire preps before you go down that road.
3. There is usually quite a bit of difference between asphalt and dirt setups. Pavement setups usually try to limit body roll in order to load all four tires as equally in the turns as possible... dirt setups usually want to induce body roll so that the right side tires will dig into the dirt. On pavement, especially with low horsepower cars, setups try to make the car stay as flat (to the track) and straight (rear tires following in the paths of the front tires) as much as possible in order to waste as little energy in turns as possible... dirt cars tend to pitch (or drift) the rear ends a bit (not as much for front wheel drive cars as you would do with rear wheel drive cars).
I can only suggest things to try since different tracks and different drivers require different settings... realize that you don't have to get a setup perfect - you only need to get your setup better than your competitors. That will take some experimentation, and also some seat time as you get used to racing. Don't allow yourself to get frustrated. You'll probably want softer (lower rated) springs on dirt, and more ground clearance (I'd start with the car's original street ground clearance), and also any bolted-on weights mounted high and on the right side of the car (firmly bolted to the door bars or roof bar of the roll cage) for dirt. Also you might want to narrow up the car's track width (via wheel offset and eliminating wheel spacers, but still fitting inside the wheel wells). All of that promotes body roll in the turns, which in turn helps make those tire edges dig into the dirt and get more grip. You'll need to pay attention to those tire edges to make them as sharp as possible, and if they wear off rounded they are probably used up for racing even if they still have tread depth left.
How much / how big should your changes be? Depends on your track, car, and driver. Hopefully you can find another race team in your class (one that is reasonably successful) who will tell you good general starting points for your situation. If you are nice and friendly and respectful they should be willing to help you get in the ballpark (once you start beating them they might get more tight-lipped). Keep a notebook about what your setup is / what was changed for each time you go onto the track (practice and all races) and what the results were. Include weather conditions, and also how wet or dry the track was. You'll need to experiment with settings, and realize that what works best for you might be different than what works for other teams. Eventually you will discover patterns in the data that you can exploit.
Although it has gone out of business, there is a magazine called "Circle Track" that had a lot of good technical advice stories. You can still find their articles via
https://www.motortrend.com/plus/magazines/circle-track/1688 . It will take some digging through the magazine issues on this site, but is worth it.
