1) I would see if you can get 8.1. I had similar issues, but having 8.1 seems to help significantly.
2) Microsoft has said they are going stop integrating the People Hub w FB. I would suggest getting off that method.
3) I would agree with you that the current FB app is still missing some features, but not seeing ALL your posts from friends might have something to do with the security settings on your FB account. Keep in mind that the FB app is not actually an FB product. It is Microsoft and such, a 3rd party app that needs permissions from your FB account to be useful.