I want to thank you for sharing your story, specially being so respectful & candid about your relationship & asexuality.
I am in a long term loving relationship with an asexual woman. I too have come to a place where I miss & want physical intimacy & passion, don't want to pathologise or keep expecting her to change, and both considering polyamory.
Lucky you have found a wonderful girlfriend who is so supportive and understanding of your love for your ex wife & it sounds like she is equally impressed and smitten with you.
Your story is encouraging & I wish you all the best,