Wow, okay there's a lot to cover here, and I don't think I have the time to do it all in one sitting, but I'll give you a few things to consider:
The first point you brought up, your need for convenience to SFO:
1. You are correct that Petaluma is a straight shot down the 101,
only 32 miles to the Golden Gate Bridge, then through SF and south to the airport.
I would add 15-20 minutes onto that 1 hour time frame because frankly, you WILL slow down considerably on 19th Ave in SF as there are stoplights on almost every block once you get south of Golden Gate Park.
While those lights are timed and can be work out well, it's definitely the least predictable traffic section of the drive.
Petaluma is a great town, with a lot of horse people, farms, etc.
West Petaluma (the historic side of Petaluma) is where downtown is located, lots of restaurants cafes bars, independent shops, boutiques.
Creative types, college students from Sonoma State, ranchers, foodies, musicians all congregate around here.
2. Santa Rosa is about 13 miles north of Petaluma which makes it closer to a 2+ hour commute to SFO.
3.Your rental budget is a bit short of the 2 bedroom average for Petaluma.
4. Sonoma County is agriculture/wine/cattle/horse country we have a whole lot of horse people around here, I can even think of 2 feed stores within 2 miles from my house here in West Petaluma.
5. There are plenty of hospitals around here Humboltrat already mentioned the Sutter ones. I have a quite a few friends that commute to SF to work at Kaiser and UCSF as well.
6. as for your towns list :
Sebastopol: Hwy 12 to 101, maybe too remote for you (not in price range)
Kenwood: very remote (not in price range)
Forestville: remote on coast therefore, not your weather, colder foggier rainy.
Novato: just South of Petaluma in Marin County, which may raise your rental costs (Marin County has that general reputation of being more expensive)
West Petaluma: I know of 2 bedroom rentals are roughly 1300 and up ( more units on the upside of 1450) so your 1200 is a touch low. But otherwise fits your requirements.
Marin: is an entire county unless you are asking about Marin City? Please clarify.
Bennett Valley: a northeast section of Santa Rosa. Pretty, but in Santa Rosa which isn't necessarily a bad thing, good hood, good schools, etc, but the geographic issue is SR to SFO.
Forestville: see above (already listed)
Guerneville: north of Santa Rosa and up on the Russian River, closer to 3 hours to SFO.
West County: usually refers to the multitude of land West of 101 Sonoma County which includes Forestville Sebastopol Occidental and Bloomfield (same issues see above)
Guerneville: already covered (see above)
Monte Rio: in the woods by Guerneville so similar situation as well.
Healdsburg: north of Santa Rosa, hotter than most other places listed, generally more expensive touristy price ranges.
Jenner: beautiful, very remote, about 3.5 hours to SFO (probably more, it's been a while since I've been up that way) colder foggier rainy rainy.
Bodega Bay: same as Jenner only a bit closer to Petaluma.
** when I mention "remote" I'm referring to the multitude of windy 2 lane country roads to get to major highway, and no Highway 1 is not a major highway
I think you should look at rental listings for more rural West Petaluma, East Petaluma,Penngrove, Cotati, and Rohnert Park for your budget.
If you can stretch to 1450 then I think your options open up considerably in Petaluma.