Hi Geoff,
Thank you for sharing your experience and seeking support for your situation.
Your name made me tear up a little bit, because life does feel like that sometimes- us against ourselves.
You sound like a compassionate man with incredibly strong priorities, which are both terrific qualities in a friend and family member. I am really sorry for the loss of your mother, I can only imagine how I will feel when I lose my mother, but I am sure she is so grateful for you for being so strong and available to her in the top years of her life.
Loneliness is very hard. Someone once said that there is a difference between feeling alone (and fine) and feeling lonely (feeling like nobody cares). There are people out there in the world that would care for a man like you in their life, Geoff, and now it's time time to find them. Here is a good start. There are also social groups online that meet up, you mentioned chronic pain so I am not sure if you can walk much but there are groups called Social Walkers in Melbourne and Vic, maybe there are some in Brizzy?
It might be worth while to use medicaire to make an appointment with a social worker and discuss how you are feeling. Social workers have a roster of community services and social groups in their toolkit to share with folks like you. Feeling lonely in your 50s is actually quite common, so it might be helpful to have someone connect you with others who are feeling the same way.
Chronic pain is no joke. Being in constant pain can have such a negative impact on your mind and body. I am guessing you have already accessed a chronic pain facility, but may have found they are not addressing your needs adequately. Physicians and nurses are afraid of high pain doses of medications now, for good reasons, but it has resulted in a lot of people's pain being undermanaged. I have suggestions for pain, but I think it would be better for you to hear from others in your same situation (it's probably inappropriate for me to suggest biomedical and natural medications to you on here). There are groups of people online who discuss chronic pain, find them and see if any of the ways they support themselves can support you too.
As for the psychological struggles, have you ever thought of following psychologists who specialize in your needs online? There are also numerous free courses online that can help someone learn about their PTSD and anxiety while providing tips and strategies to harness your mind. I also recommend Boho Beautiful Meditation's channel on YouTube. She and her husband Mark have some really soothing and grounding meditations for anxiety, stress, and loss of connection to life.
You sound brave, thoughtful, insightful, dedicated, and hopeful. Five really good features that are very promising that, with a little work, you are going to find a way through.