I'll try to answer your questions point by point.
First though, let me welcome you to the game.
Now, before I go on, I'd like to note that this game is very faction-oriented.
1) As such, yes you are able to go freelance, however, the first few months will be harder for you. Reasons for this is because you need to accumulate some some kind of way, which in return should be enough for you to purchase your own vehicle or ship. The easiest way of obtaining items without joining a faction at all would be by accumulations of CPs, or Combine Points. After having a certain amount, you can exchange them for vehicles, ships, or other things. However, if you do not intend on donating to the Combine (which will reward you with 1000 CPs per dollar you donate), then it will be a long time before you will be able to accumulate a vast amount of wealth by new player standards.
2) Leaving the city is possible by way of two methods for you currently. One way is by way of the good old-fashioned feet. Simply walk. The other way would be by vehicle.
Getting a ship to get off-planet will take a while if you do not intend on joining a faction. However, you can hire a private transport company (a good number of them are available in the classifieds section), but they charge money, which in turn you may not have. The easiest way to raise credits is initially to join a faction.
3) I am not sure how many force users exist, but my guess would be somewhere around 5%. That doesn't sound that much. That is because that is not much.
In order for you to find out if you are force-sensitive, you will need to ask force-sensitive users to test you for your force-probability. Don't get depressed if the answer you get is a No, it most likely means that the person you asked is simply busy. Ask someone else in that case. I dare say it is a golden rule that the best chances of being tested is when you are in a faction, but time and again this rule has proven to be inaccurate. It just depends on when and how you ask whom.
I think that answered everything. All in all, it won't be easy to start off alone from scratch, but it is possible. You will have to endure more patience, but if that's the road you want to choose, then by all means, take it.
____________Time to go to war with the Flame Tigers