So would it be better to overstay and then pay a fee at Ezeiza when leaving, and risking getting banned for returning, rather than doing visa runs?? Or would overstaying get me in as much trouble as doing a visa run?
Yesterday I thought you were still in Europe and concerned about what could happen when you tried to return.
Based on this post, it appears that you are actually in Argentina.
If that's the case, you obviously don't have to worry about returning to Argentina by bus at night, at least not yet.
If you make anther visa run by ferry you will get an exit stamp on the way out.
Though it seems less likely to happen if you leave by ferry, you could also get the five year ban then.
If you are denied reentry at any border crossing and you then return at night when there is no border control there will be no entry stamp in your passport that follows the last exit stamp,
It will be as if you reentered illegally and that will make you subject to the maximum overstay fine the next time you leave.
In my opinion, the best "solution" is for you is to stay in Argentina and apply for residency or citizenship.
If you don't qualify for the visa rentista (among others) to get temporary residency you could consider marrying your partner and applying for permanent residency.
You can also apply for citizenship (it isn't "simple" if you don't have a DNI and at least $6,000 USD to pay a lawyer) and that should protect you from deportation by migraciones, but it might not be advisable to leave the country until your citizenship is granted.
PS: Bajo_Cero2 (who is arguably the best citizenship lawyer in the country) has told others to apply for both residency and citizenship at the same time. If you are married to an Argentine citizen, that would be possible, but there's no guarantee that migraciones will grant the permanent residency based n the marriage.
The DNU/2017 apparently gave migracnones "police powers" and that means individual border agents have the power to be as strict or as lenient as they wish when applying the laws.
It also gave migraciones control of the citizenship process, but Bajo_Cero2 (aka Christian Rubilar), working with other attorneys, challenged that provision of the decree and control of citizenship was returned to the federal courts.