New Style ESA application for newly permanently ill health retired person.

I am 35 years old and, on 31st May, I was permanently ill health retired due to MS. I now receive an occupational pension as my previous employer considers that I am ‘unlikely to be capable of gainful employment before my Normal Pension Age’. (Gainful employment means paid employment for at least 30 hours a week for a period of at least a year.) Therefore I have applied for new style ESA.
However, despite sending in the application form and supporting documents (including copies of fit notes previously submitted to my former employer), the DWP texted yesterday asking me to submit fit notes from 1st June. I am confused about this. However, my GP has issued a fit note today, citing ‘MS’, which is valid from 7th June for 3 months. To further add to the confusion, today I’ve received notification that I have a WCA online appointment booked for Monday 30th June!
I’d be really grateful if you could advise me on the following:
1) How should I handle the WCA appointment on Monday? Presumably by stating that I’m permanently ill health retired, in receipt of an occupational pension, but that I hope to work a few hours a week if possible (less than 16).
Should I be concerned about the WCA? I don’t want to harm my chances of success.
2) Do the DWP need me to submit fit notes or was their text sent in error? If not, I won’t send them the one which my GP issued today. If they do in fact need fit notes, is this likely to be for the entire duration of my benefit or just for the 13 week assessment period.
3) Does the 3 month fit note issued by my GP today help or hinder my application?
Thank you so much for any advice you can give.