Yes it does make a difference - chins have extremely sensitive digestion systems and you want to stick with a trusted feed. If you can't get the Manna Pro Show, I feed Purina Rabbit Show Chow and I get a 50lb bag for $18 at the feed store. It's excellent feed and usually available. I personally wouldn't mess around with an unknown feed.
I know they are used to the treats but you wouldn't let a kid eat dessert everytime he or she wanted to right? Moderation is key - try offering sticks - I know you said they were expensive at petstores - try the classifieds here...I recently paid $12 for a pound of applewood twigs from Rhonda and my chins love them! My chins only like the small thin ones they can destroy immediately. You could also try offering a different type of hay as a treat (orchard grass is a good one). You could also give them their dust bath as a treat when they go back into the cage on their own.
Please take that log out - it's bad news - its held together with honey which has loads of sugar in it - back to that bacteria, gas and bloat situation. Anything with sugar in it is bad. They can chew on hanging toys, lava ledges, shelves instead.
I have to say something about those ramps - those are a broken leg just waiting to happen. Please take those out ASAP. You can use wooden ledges as steps for them to get up to the other levels - I think Alli from Camphor Chins sells them for $5 each.
Most people give up on putting the hay in bowl since the chins usually end up peeing on it - I usually just put it on top of a house - I do have a couple of hay bags that Alli from Camphor Chins makes that are great!
As far as the living arrangement - if it were me with what you've said, I would rehome Sophie to a home with another female chin she might get along with or a home where she could be spoiled as an only chin. Don't get in over your head. It's better to have an appropriate number of pets so you can afford vet care and be able to spoil them a little bit. That would also eliminate the possibility that fighting over her in heat would happen.
Agreed on the back yard breeder comments, unfortunately there are tons of them - chinchillas are not a real 'mainstream' pet so vets don't see them too often which makes most of them unreliable sources of information. You are in the right place - several people here have DECADES of experience with hundreds of chins and some are highly experienced pet people. One thing is assured with members of this forum - we are definately here to steer you in the right direction and for the chin's best interest. Read, Read Read! There are tons of threads posted on the things you have been asking and receiving advice on
you'll see we told them the same things!