Firstly sorry to hear this. It must be very stressful.
Realistically the next step is to reapply when possible. The legal steps will take longer than another application.
The next step is an upper tribunal, but it must be shown that the FTT made an error in law. This means,
You could also make an application for judicial review if the DWP made an error in law.
Neither of these apply if you simply disagree with the FTT decision. Both are legal processes which require professional advice and both require permission of the court to pursue. The JR process is practically a non starter but the UT one may be possible.
https://www.scope.org.uk/advice-and-support/further-appeal-upper-tribunal/