Hi Sensa2004.
Welcome to our Mattress Forum! 
Thank you for following our Mattress Forum Rules and for your full disclosure… I appreciate it.
Sorry to hear about the joint pains… I hope the new mattress will help a bit. I appreciate you taking the time to share your experiences (with both mattresses) and I am sure that many visitors will find your comments helpful. As far as donations go… I very much agree with you…some companies are more environmentally aware than others and some chose to disregard the subject altogether, but the good news is that the trend to minimize the footprint and keep returned mattresses away from the landfills is on the rise, and businesses are taking steps to either donate or recycle old or lightly used mattresses. It might be interesting for anyone interested in the subject to read through this article here by Sleep On Latex, one of our environmentally conscious Trusted Members., or another article here by Parklane Mattress - another Trusted Member.
I look forward to any updates you might have once you’ve had a chance to sleep upon it for a while.
Phoenix