Check the website;)

If you can avoid it, dont leave luggage or items of any worth visible in a vehicle. But if you dont have a choice, try to hide it as best you can. Parking garages might be a better choice then on the street. And if have to park on the street just try parking in a high traffic area so if something suspicious happens other people presence might make it not so comfortable an environment to break in. Its a risk. But near the ferry building i usually see a lot of cops so your choose in the end.

Park on Soma, take a nice walk. No parking there. There's paid parking lots up the street, too.

The building closes at 10 p.m. but the shops close at different times

Yes

I used to work in the building not long ago and can confirm there is no luggage storage in the building.

Depends on what you want to buy. If you just need a memory card or common charging cable you can go to Walgreens which is nearby.

Yes