I definitely think that you can work with her, but it's going to take some times for you both.
I would definintely amp up the exercise though. While I don't think walks are usless, as some do, I do think that a puppy with this lind of energy needs to be exercised way more. I mean honestly how tired are you after these walks? Just think how much more energy she has then you in general and ask if you think she really is tired after. So I while she's young, and you don't want high impact type activities for her.. maybe a walk in conjunction with a good game of fetch where she's sprinting to get her toy would tire her out much more.
She is also still so new to your house that I think you need to focus on bonding and building your relationship with her. I have never rescued, but I have heard may people start with a 2 week shutdown, maybe that is something that would help you in this situation.
In regards to the tail chasing. distract, distract, distract!!! This I do have experience with. Titan was an avid tail chaser from about 4 months and on. Luckily he didn't bite his tail, he'd only catch it and repeat. BUT he was doing this for 2 reason. The most common reason, is he was being understimulated. I had a routine similar to yours and it just wasn't cutting it. He was essentially going stir crazy and trying to find a way to tire himself out so he became obsessed with chasing his tail. The second reason is anxiety of sorts. He isn't a nervous wreck dog.. but when he gets into a new environment or there are and overwhelming amount of new people around.. he will begin to chase his tail until he is comfortable.
I dealt with this by distraction, either play or command with play. When he would start chasing his tail I would stop him and make him lay down. When he layed down we played or I treated him. Mostly it was distraction with play. Timing has to be right though. There was a time where he used it to get my attention because he knew I would play if he did it. I started to have to give him commands before playing so he knew he was being rewarded for listening. It takes time and patience with that one. He used to sneak off to do it, and still does on occasion... Also, look into vinegar or bitter apple to spray on the parts she bites, thay may deter her. Here are some links from when he started his tail chasing...
Advice: Tail Chasing Obsession
Help.. anxiety and tail chasing..
There was some great advice in those threads about that.
For the shadows, I'm really not sure, I almost would say that distraction is key too. You dont' want to keep her inthe dark all the time so she is going to have to get used to it. As stated above, some dogs do need medication, but not all. If you have the time to work with her, you could be really successful with consistency and dedication. Do you know her history or anything?
My suggestion would be if you don't have time for her in the way she needs, then return her and note ALL htese things so they know about them and can place her in an appropriate home. That and also that she doesn't like cats.