I am lost

Does your husband have a preference for where to move to?
Do you hope to move abroad?
If you are going to stay in the UK, I think it'd be best to stay reasonably near to your sister and repair your relationship with her, if you can.

Definitely some mistakes in the age and military years etc unless this lady was a very very young bride perhaps she meant she is 74 not 64
Moving unfortunately won’t make you friends
What does your husband think of moving towns / countries at 80
Would you be out any more if you moved somewhere else ?
If you moved to US or Australia they don’t have a NHS as you both get older and you may need a health service more
Lots to think about

at least you have your husband with you.
much of your post sounds as if you live alone.
can you not make peace with your sister and meet her for walk in park.
good luck.

Do you consider your dh to be family?

How is the relationship with your sister? Any chances you can see her outside her home?
May I ask what happened and can you make amends?

Not sure what the actual problem is
Finances?
Location?( Moving later in life is not always easy, especially where one partner is 80)
Not having friends.? (Moving to a different area wont necessarily solve this either )
DH has been working away from home? (Not recently, presumably if he is 80.)
That your children live abroad is something with which many others GN can sympathise and might have advice on coping with this
You say you miss your family but your sister lives locally, so why not meet up with her on “neutral” ground eg for a coffee? If she has close family - are they not also your family?
Everything seems to be getting on top of you and I do think it would help if you could prioritise the things you can change and the things you will somehow have to learn to make the best of.

Perhaps it is a typo, lemongrove, because it isn't possible.

Can you meet your sister outside and I wondered how you got on with her family? Your BIL doesn't have to be there. How does your DH get on with your BIL and DS?

Visiting family overseas is mot possible yet but we can hope it won't be too long before we can go again. You could start planning (if not booking) your next trip Jeannie..
In the meantime, can you and your DH get out more?

Jeannie
You say you moved to that area 30 years ago, when your husband left you ....and you are now 64.That means that you were then 34 years old.How then, can you possibly have been a military wife for 20 years up to that point??

Poor you. Loneliness can be soul destroying. Is there anyone you can talk to, someone who will listen and not jump in with their own worries?

Big hugs ?

It's horrible to feel lonely. It can be very reassuring to be part of a family. Do you feel reassured that you and your present husband are a family?

Do believe the bird in the hand is worth two in the bush?

jeannie I don’t have any answers I’m afraid, but I couldn’t leave your post without expressing sympathy. It’s very hard when family are all scattered in different places at the best of times, but lockdown has made life more difficult, depressing and inward-looking for so many.
Is there any chance of re-establishing a closer relationship with your sister?

Jeannie lots of us on here with DGC abroad, many long distance like me and you. I too used to go over to Oz and spend a month there enjoying my family and the DGC. For this year this is off of course and at times I feel I'll never be able to visit again. But we must keep positive and look forward to the future.

I really don't have any advice here but am sure someone will.
Just wanted your post to get noticed.

Does your husband have any interest in moving? Or maybe he is wanting to stay near your brother in law?

Do sorry you are sad.