1. Yes, but as someone applying via a similar degree relationship (I'm married to a natural born Argentine citizen) my naturalization process has taken almost 2 years to get towards the judge actually reviewing it, and I have no guarantee it will wrap up before the end of 2023. There are numerous pros, and no cons that I'm aware of for getting your permanent residency while waiting for your citizenship, plus having a DNI will make your guys' lives 10x easier, plus you'd be free to enter and leave the country with less headaches since you'd have a regularized migratory situation.
2. Bajo will know this more than any of us, but 18 is the letter of the law, but I'd be surprised if there isn't a case he's familiar with in which it might be possible to apply for before hand - again, not something I can speak to. He's a lawyer that specializes in immigration and citizenship, and if you don't plan to get your PR while waiting for your citizenship, you basically have to go through him, si o si.
3. You're setting yourself up for problems with AFIP/UIF by declaring to a judge that you have foreign income, but not using the MULC to settle these funds. That being said, given the odds 66% to 33% that Comunicación "A" 6770/2019 gets revoked in December, it might be a non-issue and you could start simply sending your earnings here, but this all depends on what happens in October and November, so I would wait until then, and from what I've heard, judges have taken WU remittance receipts as proof of funds for sustainment. This is also why I recommend getting the DNI while waiting anways as you'll be able to become a monotributista and build credit here while waiting to become a citizen, and use your registration with AFIP as a proof of having a job/means to support yourself and family, and same with your spouse if they are working.
The important thing to remember is that the process for citizenship is going to take a long time compared to me and others as we started before the Russians and Ukrainians came, and it was already slow then.
Also, what country do you, your spouse, have citizenship from? If it's Russia, Ukraine, or any CIS States expect it to take even longer too, they're really scrutinizing applications from these folks.