Hi Mike,
Congratz on your first Whitney attempt & hopefully summit...
I'll try to address some of your concerns without going over my character allotment.....
I'm not sure if Ursacks are even allowed in 'active bear areas'. There is a bear vault that is smaller & lighter in weight than the Garcia. Bear canisters are required & can be rented at the Portal Store, the Interagency Vistor Center where you pick up your permit, or from the store Elevation in Lone Pine......
Bears can be active in the Portal area. But on the trail it's the marmots/chipmunks that will get into your unattended pack & tent that you need to be aware of......
Ha ha but I have to tell you, we were camped in the Portal campground last week, inadvertently left the bear box open overnite, & were shocked that nothing had ransacked it....
Yes people all the time leave their setup at Trail Camp while they are on the trail. Not an issue. But I have seen where folks will collapse their tent, or otherwise leave it open so the critters don't chew a hole in it to check things out......
Leaving TC for the summit, I would leave as soon as possible in the morning. As a first-timer you will want to 'savor the experience' as it were, so it will take you longer to summit because your are pausing to, 1. breathe, 2. take photos, 3. just experience the journey. The first time is just so overwhelming....
Actually, to me, every time I go up is overwhelming. & different. So sometimes I like to stop & just take everything in......
As for being 'solo'...You are never solo. Except maybe in the dead of winter. There are so many people on the trail.
As for parking, there is a campground at the Portal. You don't need reservations if you get there early enough in the day you can get a site. There is a walk-in 'hiker' campground site. & some people spend the nite in the overflow parking area, altho that is not encouraged....
With the road construction & parking restrictions this year, there has been no issues getting a parking spot at or near the TH. You will be issued a parking permit with your overnight trail permit.....
Hope this helps. You can PM me if needed.....
Have fun!