Hi Carole,
Bear in mind that DLA, unlike ESA and incapacity benefit, isn't a test of how long you can or can't do something. It's about attention - or supervision - it would be reasonable for you to receive in connection with bodily functions.
So, being unable to sit would not necessarily, in itself, be relevant. But if your husband would benefit from help with things like using the lavatory because of problems with sitting then that would be relevant.
Not being able to sit might also mean he needs help with things like bathing, dressing, getting on and off sofas if he has to lie on them and so on.
But you would know best about all the help your husband gets or would benefit from because of his condition.
Good luck,
Steve
Nothing on this board constitutes legal advice - always consult a professional about specific problems