Controlling someone else's iPhone remotely is pretty much impossible. Change your Apple ID Password if you think your partner is doing something --> Change your Apple ID password - Apple Support
Then change all your other passwords for apps, such as banking etc.
Also, while you're at it, change your iPhone Passcode to a code he won't know (but make sure you jot it down somewhere for easy recall if you forget it --> Set a passcode on iPhone - Apple Support
If you don't already use Two Factor Authentication, set it up immediately --> Two-factor authentication for Apple ID - Apple Support
Then don't share the new passwords/passcodes with your partner. Maybe dump the partner if you have to be this concerned they are doing nefarious things to you. Your choice on that of course.