Like most manufacturers, they seem to try and uses any excuse to wriggle of a warranty claim if "unauthorised" servicing is done. They'll do this whilst the vehicle is in warranty. Honestly, as they are offering 50% against a vehicle that's now 2 years out of warranty, I think that's the best you'll get. You can try and get a bit more out of the dealer, as I said< that's probably your best hope. After it's fixed by a Mazda dealer, you shouldn't have the same issue again. I've been following this topic since mine failed and have never heard of anyone who's had this happen twice.
As for onward servicing, I can't really advise as mine have all been company cars so have to be dealer-serviced.
Alan