Since you already deleted the project, you can probably fix the app issue by launching in airplane mode and clicking Settings > Account Sync > Reset Local Data, then turning off airplane mode and letting the app sync. That will do a fresh download from the server, not including your newly added and deleted project. Alternatively, you can delete and reinstall the app, but then you will have to reenter your login info and some other settings.
If the app still crashes, please update your help ticket with that info.
I don't think the download speed could make the app crash.
To undo deletions from the website, you need to select each of the items you deleted. You can use the filters on the left side to show only deletions, and look at the dates in the list to find the batch of songs you're trying to restore. You do not need to undo the updates to restore a deleted item. However, if you had documents or recordings attached to your songs, you would need to undo the deletions of the songs, the documents and the recordings.