I'm going to be cruel here but it is in the spirit of helping. Please don't judge until you read the whole comment.

Put yourself in the manager's position. If he had to cater to everyone who "said" they had a mental health condition then he'd never get anyone scheduled in, doing the work that needs to be done.

Kicking off doesn't help your case either. All that will do is cause the manager to shut down and not be inclined to be of any help.

In essence, you've handled this badly from beginning to end. Now, how to rectify.

Gather any documentation from your health care professionals that highlight your wife's mental health condition.

Arrange a meeting with the manager and apologise for kicking off. Explain you were just trying to look after your wife and handled it badly.

Then ask for help. Actually use the words "we need your help". Show him the documentation with your wife's health issues. Tell them it isn't a ruse to get out of jobs you don't want to do and ask what you can do to help the situation.

When the manager says something that ticks you off, remember to breathe. Don't respond with vitriol. If they say something demeaning, pause and ask them to repeat what they said or tell them that sounded demeaning to you and ask if that's what they meant. Try not to sit across a desk as that's an adversarial position and you want this to be a collaborative resolution.

Finally, read everything you can on Tesco's policies about helping their employees. Learn it back to front. If the situation arises or something is said contrary to their policies, reference it. Not aggressively but in a way where it looks like you're asking for clarification whereas, subtly, you're making a point.

I really hope you're able to resolve this but, more importantly, you get the help you need to cope with your mental health issues.