As you know they have to follow a certain procedure, including giving you the right to be accompanied by a colleague (who could be a union rep) and giving one or more of eight specified reasons for refusal.
It does sound as though they may not have followed the right procedure, but they did offer two compromises.
There is no obligation for them to accommodate your request just because an OH doctor thinks they should I'm afraid. Changing work patterns to help someone off long-term sick back to work is something different, and if you had been off ages and they were considering dismissing you or something similar, and had refused to make adjustments that would allow you back to work, then that's something else. But that isn't the situation here as far as I can tell.
When you say 'do you have a case', what do you mean? A 'case' for what? You mention indirect discrimination, and 'marital' discrimination (not sure what you mean by that, you don't have any particularly protection against 'discrimination' for being married, or not married, or whichever you are). Are you thinking of making a claim for indirect sex discrimination?
You mention that you have put in a grievance for all these things, but have you put in a grievance about their failure to follow the proper procedure? A tribunal can hear a case about that, and can insist on the request being heard again using the correct procedure, but it can't tell the employer whether they should accommodate the request or not. So if your request is not accommodated and you want to take it further, sex discrimination will be your option.
Based on what you've said it's impossible to say whether you have a case for that. Refusing a request which, in your opinion, is manageable, isn't necessarily discrimination. What reasons did they give for the refusal? When you requested to work from home 10 hours a week, presumably you would have childcare in place for that time?