This is a real shame and although I want to believe you are just winding us up I get the feeling you are serious on this.
Sometimes it is better to chuck in the towel as you are putting it. It really is unfortunate that it has been so difficult and the amount of time you put in.
Is there anyway around it like not wearing it and using it as a puppet?
A head with neck and shoulders and an arm are all you really need if you have that you have a veracious Wampa!
I am trying to cheer you on not bog you down you know. There’s always another way, but I don’t wish loads of work on you… But we all know you want to make it work. But I guess you also want to finish, everyone understands that.
Nobody will be upset if you do nothing about it but people will wish you had a go no matter what the outcome.
Take a look at Jaws that did not work until they had nearly finished shooting. What did they do they put a model fin in the Water Until they got it working right at the end. Even the Wampa itself you see very little of it and you don’t need to… But you can get in close even Blurred out of focus like a disoriented POV shot or something tricksy and cunning.
My advice is just Go for it think small and try to get big results… If you really, really want to call it a day nobody will hold it against you.
Edit… One more idea to perhaps try and make this work is to film all actions slowly and speed them up giving it that hyper realistic feel often employed in Monster films. Not sure if that would be a solution but hey I am trying to get you to look another way at it as it does not seem like from what you said 2 more months not an option.