Drive. Or taxi.

Yes. For the most part the dogs have been well behaved and the owners have control of the dogs (clean up after them as well). So go enjoy and be responsible.

The Muni Bus line 29 takes you most directly to Baker Beach, the bus line terminates there. The line runs from early mornings to right around midnight, 7 days a week.

There is parking on the cliffs above which I would imagine you could park for the day but no to sleep over night.

We visited during the US Government shut-down of 2018. The Presidio was open. According to the US National Park Service website for the Presidio, it is open 24/7 and there are no entrance fees.

Didn't see anyone sea bathing so I guess the other comments here about the temperature of the water are true. If it important to you then I'd suggest going to the beach by the old Sutro's bath complex or better still somewhere like Carmel.

we were not driving but there was a lot of spots along the road very close to the beach

I do not know 100%, but most Cities have ordinances which do NOT allow overnight camping unless in designated campgrounds, with facilities, which this is not- It's just a parking lot to access the trails

Could be on the cooler side, but it is not unusual to get warm, sunny weather well into the fall (TIP the fall is the best weather season in SF). That said, it could also rain. I have been on Baker Beach in sun, fog, and rain (I frequently included Baker Beach in my weekend long runs) and I have enjoyed it in all weather. On average, you odds for decent weather on Nov 4th are good.