Dextrose for sugar cat on remission?

Hey,

my sugar cat is on remission. He has some issues with loose stools, the vet reccomended this food:https://www.apotea.se/specific-fxw-adult-7x100-g
He eats Bozita wet food now.
But it feels that the vet is not really reccomending enough...we have tried fortiflora for a month but no big difference.

I was reccomended that in another group (my cat is also Fiv+):
https://www.vetsend.co.uk/protexin-pro-soluble/#

Can I give this to him? This are the ingredientes:
Dextrose, gut flora stabilisers, protexin probiotic, enterococcus faecium.

Do you have suggestions otherwise? He has had loose stools that gets better sometimes forever.