Morning Mrs. K!
That is really shocking to read. No wonder your husband's health is so affected.
I'd suggest MrK goes to GP asap and tells him/her what has happened. What is amazing in all of this is that despite some terrible treatment from his line manager,your husband has a great attendance record. It can't really be argued at all that he is not up to the job health wise.
It might be a struggle to get through to some of the help lines this morning but do try and ring MIND, they are lovely people.
If work tries to contact husband further, is it possible for you to step between and deal with them directly and should say that he is not available to speak to them.
Also, if he writes down as much as he can recollect as to what is happened. This will be pretty upsetting ,I know, as it starts to show how awful it is but also will help for reference if he decides to take action.
From what you have written he has been also bullied, harassed and victimised in this job. He has made his manager aware of his condition and there has been no attempt at all to make any accommodations for him . His only time off has been due to physical illness or because of a family emergency.
All their actions seem to be directed at making him more unwell.
The onus is on the employer to show that they treated him well. I doubt that they can do that at all!
I'm really cross reading about his treatment and I am a complete stranger!
Send him my best wishes. He has been shabbily treated and I hope that you get advice.
If he is leaving on 13th then they are not obliged to pay him if he does not return. However, he could send in a sick note until that date. If he can manage, do not go back. You have 3 months less a day to lodge a case with a tribunal for disability discrimination. My gut feeling is that they would make an offer of compensation prior to appearing at tribunal. How it goes forward depends on the size of the employer and nature of work etc., and I know it's best not to put that on a public forum.
Hope things go your way today when you speak to people.
ACAS also is a good place to start. Apols for the typos, 2 year old keeps trying to close the laptop lid and shouting NO! 
www.acas.org.uk/index.aspx?articleid=1859