Sending a hug
hope writing your post helped you get to sleep
Try not to worry about the friendships, friendships often bud and blossom at some of the most unexpected times. You may find you are the minister now, but when you retire you will have that link with people, they will know/recognise you and when no longer the minister may find you can develop some into friendships, starting by perhaps a suggested coffee when you 'bump' into people.
With the caring you have done, you may find that is important to you, and you could consider some involvement in some way with charity work when you retire (if you want to of course!), for an example. Even if just an hour a week, that would include interaction with people, and wherever there is interaction there could be a potential friendship waiting to bloom
When i came here I never expected to feel such part of the group or to make genuine friendships. We have a meet now and again, and following Bristol it looks like some smaller meets will be happening in various parts of the country, so if one comes up which you can get to I'd recommend it. Will be nerve wracking at the start, but within minutes of each one I've felt welcomed and relaxed. You never know but you may meet friends there
When you go part time, have a think about any interests you'd like to pursue, any hobbies like photography? Where I live theres a place which does all sorts of courses throughout the year and that would be a good start for getting to know other like minded people too, whilst progressing a hobby or learning something new
You also have online options, another place I often recommend is Future Learn. Its owned by the Open University and has a large amount of courses on a wide variety of topics, provided by universities and they are free. With the courses they encourage you to get involved with other learners, with comments, and can get into discussions on topics.
Hope i havent babbled on, just a few thoughts to show some of the options and hopefully help you to alleviate some of your concerns a bit xx