I think that only sad news are available.  :-/

First of all, the box vendor is the only one that could issue refunds. Not CS, they only sell downloads here and refunding them is generally not available, though may be an item of asking for it. As said, this does not affect any boxed products. Box goes to the vendor of that box, legally correct though sometimes not that easy to accept.

Sad news two, the same applies to the updates. The 757 is 4.6 now, the 767 is 1.5 but if you are running any box (except for the another company 767 one), you can't access them. That's not something I'm too happy about, but I may add that, again, the vendor of the boxes has to make sure that he can access updates through CS itself for his customers.

That's a business to business agreement and therefore two sides are involved. So if one refuses to set up a proper agreement, the customer can't get updates. another company for example did, so their customers can access proper CS updates. another company and Amazon may not have such an agreement. Means no update path available there.

On the actual problems. One source of wonky autopilots with the 4.4 and 1.4 releases has been an outdated or faulty FSUIPC installation. You will find quite some stuff when searching these forums, so please stick to the threads.
If you don't find anything (which of course means that you've tried), feel free to ask.

I can fully understand that a wonky behaving plane isn't able to produce fun. I had 4.4 running fine and 1.4 too, so there's a chance that your boxed software (being the same version, 4.4 757 and 1.4 767) will run fine too. As for the refund. Read the above, wrong place to ask and look for one in terms of boxes. Sorry.  :-/