I'm not sure that archive.org can help: it is uncertain if/how many pages they have after March 2nd, and the rest (SL archive etc.) is off-limit to bots & crawlers, so archive.org won't have any other data. Right now it looks like that Bing has the most recent versions. If you have a page that was edited in March and which you really care about, compare Bing's cache with SL's version.
Donations: SL is not that expensive to run. With added backup space it is now about $100/month, which I can afford. Even if I could raise several thousand dollars, it would not change SL - unless I'd raise so much that I could quit my job and focus my attention on SL exclusively

That is highly unlikely. On second thought: if you're a millionaire looking for a good cause, talk to me!

If you would like to help out, then why not do some
LibraryWork? I know that SL is no longer the cool kid on the block, but it still gets 1mio pageviews/month (not counting any robots.) So: help the community at large, contribute and feel good

Time to catch some sleep - I had a busy weekend...