Forgive my intrusion into your conversation, but I saw you hadn't received a reply to your question about losing pics, etc. if you delete that existing tree on ancestry.com.
This is not a definitive answer, but I'll share what an Ancestry.com customer service person told me about it during a phone call with them last week. My situation was that I had 2 separate trees for separate surnames. I had finally found a common connection via marriages between the two trees and wanted to merge the 2 trees of possible, rather than work on them individually, now that I know they form the same tree. Well, I was told we can't merge our trees, so the best thing to do is just do a new gedcom from within my RootsMagic, one that includes both families in the same tree, with the links intact, then just upload a new tree for it and then delete the two I had replaced. He told me that the only real problem is that when I delete the 2 existing trees I'd had there, that the pics and stories would also be deleted. So if I wanted those pics, stories, etc., I'd have to reupload them to the newly uploaded tree which merged the two previous ones.
I didn't follow up on that post, as I didn't have any pictures or other items in those trees yet, but from what he said, it sounds like if you delete a tree, you also delete any pics, audio, etc. that might be there.
Hope that helps.