It has been discarded as an idea already, but pithing needle is awesome AGAINST survival. I really mean it, it's painful to play against it, can name any of the 2 engines and stop any amount of copies with it. In regards to card advantage, wfain is precise there, if you want it you can get more copies of squee. And wonder is awesome. I think I'd rather cut one of the combo creatures (VV, rootwalue and hollow one) than the copy of wonder. It does... wonders.
One thing I'd recommend you to be cautious about. Don't consider good results as necessarily an indicator that it's a good version of the deck. I'm not saying it's not. All I'm saying is that survival is an awesome deck, and it's way above the median of the vintage decks. The deck is so good that tere are bad versions of survival that can do fine in the metagame. I think for you to really be able to understand and brew correctly it'd be good to play the other versions of the deck. See what works in each of them, and what are the metagame each one is better at. For example, for me there are 2 builds of survival that are insane, and each one of them works better in certain enviroments. And each one of them has it's own pros and cons. Besides looking for a better version (say a version that is better than A against any deck) you can look for a version that goes better against X and worse against Y.
I don't know how you feel about that, but we already talked about something between 5 and 10 versions of survival in the main thread. Maybe it would be a nice discussion to have there too, as the versions have lots in common, and maybe when talking about one of them we can have ideas for the other one.