In my book a 'sad sack' is someone who sits on their arse and does bugger all to improve their lot in life.
Obviously, your dh once had some get and go to the extent he went on holiday to Cuba where you met and he was smitten willing to forego his career in academia in order to move to the UK to be with you.
I'm guessing this came about because you weren't willing to go live with him in Canada even though your dc were adults at the time of your marriage.
After 9 years of UK living, he's had enough and I for one don't blame him.
Frankly, Reg, you sound as if you've got one foot in the grave, sinking into premature old age whle waiting for the inevitable.
I get that you've got a new dgs and most probably you'll have more in the future, but you can be a much loved dgm who Skypes at least once a week and flies in a couple of times a year to spoil her dgcs to pieces.
Why not give Montreal a whirl for a couple of years? It's a vibrant city, French isn't a particulary difficult language to acquire, and if you relocate south of Montreal towards the Vermont border you'll find no shortage of solely English speakers.
If you don't feel that you can raise your game and support your dh in re-establishing his career in the country of his birth, let him go now with your blessing.
Alternatively, you could encourage your dh to look for a teaching post in the private education system where there tends to be greater emphasis placed on orderly conduct, or consider relocating to France,
However, this may not resolve the question of his future pension entitlement and I get the feeling that you're unwilling to consider any move from your present location. If this is the case, you are best advised to set him free before he begins to resent you.