About Argentina. I just wanted to explain why I was worried, since how government treat immigrants in Sweden is the only experience I have in these questions. So should I be worried they take me and send me home if I appear in the immigration office?
Actually, if they are still enforcing the DNU 70/2017 they might "arrest" and hold you while the police goes to your "domicilio" to verify your home address (and someone would have to be there to do so). Then you might be released, but I suspect your troubles with migraciones would continue from that point forward.
That being said, why would you "appear" at the office of migraciones after you have received "legal advice" from "a local specialized attorney at Law"
not to do so?
If you can get married
without a current/valid 90 day visa you may then be able to apply for permanent residency based on your marriage, but, as you have already been living in Argentina for two years, it might be "wise" to apply for citizenship at the same time.
If you can't get married without a valid 90 day visa then it might be wise to apply for citizenship as soon as possible. You don' t have to be married to obtain Argentine citizenship! Unless the requirements for citizenship have changed recently, you will have to demonstrate an "honest means of living" even if you haven't been working in blanco.
And, instead of waiting and worrying (and continuing to ask questions here)...
I will stop by the Registro Civil office some day and find out what they have to say about it.
...I suggest that you go to the Registro Civil
tomorrow and learn the requisites for getting married in Argentina. Then come back and tell us what they had to say.