Applying for residency in Portugal

Okay. So, let me start with the basics.
I have been in Portugal for 2 and a half months, I’m from the UK. I’m a bit concerned about hitting the 3 months mark but after speaking to someone on the ‘brexit line’ from SEF, I have until the end of December to stay here.
It would be great if someone could clarify that for me.
The reason I have not applied so far is because we received mixed information from the consulate but upon checking, we’ve received other contrary information.
My parents own land, I am 30 years old, they’re residents. My aim is to apply for residency and become a citizen, so far, my understanding is that I have to take the normal route, regardless of my parents position.
So my first task should be to get a fiscal number + social security number and then apply for an NIF to register for self employment, once I have the NIF, I can then register for an expression of interest under article 88, 2?
I don’t know what happens past that point.
Is this all correct? Please let me know if anyone has any questions and I really appreciate any advice offered.