I don't have all the answers, but want to say I am so sorry for what your going through.
On the kitten: you're right, I think— the kitten needs more social interaction. Any piece of string, perhaps with a bit of cloth tied to the end, can be dangled while you are sitting on the couch. You might consider a mani-pedi, nipping the sharp tips of those claws, to keep damage under control. Ex might reasinably be asked to invest in a few toys, including chew toys. You might search for "Jackson Galaxy" on YouTube for helpful videos.
It shouldn't be your responsibility, but it sounds like you've tried getting Ex to take responsibility. Sadly, like the kitten's tenancy seems tied to your own. That sounds like manipulation.
Your physical health and long-term possibilities are, of course, adding to your stress. It sounds very overwhelming right now, with so many changes in your life. Would Ex consider paying for housekeeping help—at least to get the pizza boxes and dirty dishes sorted out? I don't know about your country's system for people with disabilities, but perhaps your social worker can help you figure out if any assistance in this area is available to you.
Thank you for the trigger warning about your desperation. As you know, I'm just an internet rando. I can't offer you all the helo you need, although I can assure you I care deeply. In the pinned resources at the top of this community's posts, there are some European resources if you haven't already seen them. Perhaps your social worker can add to them (and if you'd be willing to share anything you find useful, you can DM me so I can have them added to the list).
Please stay alive. So many things have changed so rapidly in your life recently. That's bound to feel like too much. Give yourself the time and grace for change.
For those who hit the paywall— https://www.zdnet.com/article/googles-new-settings-let-you-remove-your-private-info-from-search-results-heres-how/