But priority is meant to give a decision within three weeks if all is ok with the application, right? So you're still within that time frame.
Not so anymore. The priority service used to say 'within 15 working days' but they've taken that part out of the description now will not guarantee any kind of timeline now.
It only says:
This service allows settlement visa applicants to pay to have their visa application placed at the front of the queue once received by the UK Visas and Immigration Decision Making Centre (DMC) in Sheffield, to commence processing ahead of other visa applications So, while most priority applications probably will still be processed within 3 weeks, it could take longer.
With this in mind will they still have to give a decision within 3 weeks?
They don't have to give a decision within 3 weeks anyway, but if an application is not straightforward, it could take a couple of weeks more on top of that.
However, as your husband was not actually refused entry to the UK, his application should hopefully still be considered straightforward.
And receiving DLA doesn't make it non-straightforward either, it just means your application doesn't have to meet the new financial requirement and so you don't have to provide as much paperwork.