Not being funny here, but it is your partner who has the problems with the dog and it is him who should be taking the dog to classes.
Classes tend to teach the owners more than the dog and from what you say your partner needs to build a relationship with the dog more so than you.
If you are going to keep the dog then your partner needs to get on with him, a good trainer will work with your partner and show him how to have a living/working relationship with the dog.
I don't honestly see the point in you taking the dog to the classes on your own, most of your problems can be cured easily, if you read the articles I gave they will help you. If you decide to go to a training class go by yourself first and observe the class, if you don't like the training (check chains, physical force etc.) then don't take your dog. Some classes may make your dog worse and you will end up feeling bad and will end up going down the road of rehoming the dog again.
A good site for dog training advice is:
http://ttlntl.co.uk they have a forum you can join and get good advice from professional dog trainers/behaviourists, many have worked with rescue dogs of all different breeds. They also may be able to help you find a good trainer in your area.
Your main problem is your partner not getting on with the dog, unless you improve their relationship I think you will always have problems with the dog.