Yeah, we can do this. Obviously the key to it is taking a bright photo in the first place. See how this photo has a white wall, pale skin, blonde hair, white clothing.
Yes, I'd say it's possible.
But I need you to tell me more about your vision. You say a white background, but how would you intend to blend that with the ground?
Please do this. I'm pretty sure you're safe, but we need to be certain.
And PLEASE take the Levels Class. Let me free you from reliance on those shitty actions. Your file has about a zillion layers when half a dozen would do, and that's not helping this problem.
Ok, can you open one of the files that have been very very slow to save, then show me a screenshot? Of the entire Photoshop screen, including layers panel and everything.
It doesn't matter. What matters is to check that you're working on 8-bit files, not 16-bit files. 16-bit would definitely contribute to the problem you're describing.