1) Is there much difference between late August - early Sept vs mid-late Oct? When do CA schools start?
Yes. The majority of schools in CA are back in session in late August/early September. If you can wait until after Labor Day to go, that's your best bet.
*note: I remember the days in school in CA when we didn't go back until
after Labor Day. Those days are long gone.
2) We are not worried about missing parades or fireworks, but would like to see WOC. Is the best bet to get a dinner pkg or FP?
I have done Carthay Circle lunch and Wine Country Trattoria dinner packages for WOC. Both have good seats. I know with Carthay Circle lunch, we got the first viewing of WOC and WCT had the second viewing. I don't remember much re: viewing for CC, but for WCT Trattoria, we got there about 15 minutes before showtime and were led to our viewing area.
3) Should we go during longer parks hours and bigger crowds ( we usually do rope drop) as long as we have a plan, or during shorter hours and smaller crowds? A 10am opening seems way too late for us to get stuff done.
Shorter hours and smaller crowds are usually best. But remember if you stay on property, you get EMH every day (either DL or DCA, depending on the day) so you can do a LOT in the first extra hour. For DL, Fantasyland and Tomorrowland are the only ones open, as I recall, during EMH, so you can do Star Tours, Buzz Lightyear, Space Mountain (I don't think Ghost Galaxy will be open then, I've forgotten when they do that overlay), but it might be Star Wars oriented now. Fantasyland, if you like Peter Pan, you'll want to rush there. Those lines are forever long.
4) We don't want to miss HM or Small World. When do they usually go down for overlays and for how long?
According to Mouseplanet:
http://mousepad.mouseplanet.com/showthread.php?212744-2015-refurbishment-schedules
Small World was closed down (in 2014) from October 20 - November 6 to do the holiday overlay. I'm still looking for HM overlay, but since that one opens for Halloween Time
5) Where can I find historical DL hours? I have a Touring Plans subscription but can only find historical crowd levels.
Here is MousePlanet's
Disneyland Resort Update for September 8-13, 2015. If you click on Park Hours, it will tell you what it was.
6) Will the new Soarin be done by this summer?
Not sure.
7) My family hated Dinosaur at AK with its jerky ride and eardrum shattering noises. Is Indy a better experience?
YES! I went on Dinosaur at AK when I went to WDW (2012) and compared to Indy, Indy is a much better ride (and story). It is a can't miss ride at DL!
8) Is Photopass a good value at DL? We use it every year at WDW and end up with hundreds of photos after editing.
Yes, although I believe they have gotten rid of the advance purchase price option now (you used to be able to advance purchase it for $69 but now you can only buy in park for $99)
9) Our plan is to do mostly counter service food and maybe a character meal and one sit down meal. Which ones are the slam dunk, can't miss meals?
Counter Service
DLR
Plaza Inn (chicken)
French Market (salmon)
Mint Julep "bar" next to French Market, although you can get a Mint Julep from the French Market too. Their beignets are yummy!
There's a baked potato place near the rafts at Tom Sawyer's Island too.
River Belle Terrace (although this is changing to a sit-down thing for dinner packages/shows)
DCA
Boudin's Bakery/Cafe: you can have them slice the the bread and put it on the side to dip your soup in (instead of doing the bread bowl). Also works for salads.
The Mediterranean place by Goofy's Sky School has good kebobs too.
Award Weiners if you like hot dogs.
Tasty Pilot's Grill (I forgot the new name), has a condiments bar that you can load up veggies for your burger with!
Character Meal
Plaza Inn Breakfast Buffet
Sit Down Meal
Blue Bayou is pretty good. Club 33 if you can get in

Carthay Circle isn't that bad either.
10) Are character greets as regimented as WDW or less formal?
Some have fast passes, some they are just there. Fantasyland Theatre/Royal Hall has 3 princesses (usually Aurora, Cinderella, and Ariel). Some are catch them while they are out, etc. But in Toontown, the characters are usually in their houses (Mickey, you can see him in his tux and as Sorcerer Mickey), Minnie, etc.