Using Migration Assistant corrupted Time Capsule hard drive
You are most likely so far down the road that it is impossible to go back.

You CAN, however, take out the harddisk of the time capsule, buy a spare harddisk, bitcopy the contents of the time capsule to the spare harddisk and use advanced forensic tools to salvage parts of the file system not overwritten by what you did so far.   You may be lucky.  A Time Capsule is essentially a small Mac using a HFS filesystem internally to my understanding.

If your data is important enough to warrant spending money on them, consider contacting a professional company.

In the future, you may want to use the "dump contents to external disk" feature of the Time Capsule.    This gives you a stand-alone Time Machine backup that you can save off-site for disasters like this.  Combined with iCloud you have a relatively cheap and simple coverage of your data.