How is SWTOR working exactly, in 2020, for premium (expansions, char slot etc.)

Hi, I started playing 2 days ago and I hate all the stuff locked toward free to play players. I searched on google and I would like to make the answers sure, in 2020, because the game is old and we find very old stuff on google. (And btw I hate the faq I have to come here instead of contacting the support in game. Every MMOs need free to play players. A low player base always ruin the gameplay. Feeling as a garbage isn't that convincing to pay lol).

I would like to have the answers to these questions :

1. If I buy the digital upgrade, do I become Former subscriber ?
2. Is Former subscriber working forever ?
3. Is that digital upgrade worth it ? Why ?
4. Does becoming premium player give us access to all the content forever or only 1 month ?
5. If yes to 3., what exactly ? Could you give a general list ? I know for the 5 quickbars, I think 15 character slots ? Chapters and expansions, what else ? Species for new char ?
6. Can we pay for 1 month only or the minimum is 2 months ? If this is 2 months, this is a very bad way to make new players. Players rarely play a single game. In my case, I would pay for 1 month then jump on path of exile asap long enough to minimum unlock the footprints (and for the current league, the hat too). 30$usd is 40.50$can and I see we have to pay the taxes so 46.50$ for a 9 years old game for only 2 months instead of buying 1 or 2 very good games on steam forever... meh... So far the game is good but meh... If we have to pay 2 months I think I'll stick to the digital upgrade if we can be former subscriber.
7. What are the former subscriber bonuses ?

8. What is the maximum lv for a free player, a former and a premium ?
9. Is it too late for me to grab a referral ?

The complete answer list for these questions shall be written from EA directly on the store page of the website... I don't understand why it isn't there after 9 years.