NTA. Your Dad is an asshole for texting and driving in the first place. It's been well established that texting and driving is just as bad as drinking and driving, and your Dad is putting lives in danger while doing so.

That being said while you have good reason to be terrified, yelling at him and slapping the phone away likely isn't the best solution. It sounds like it's time to sit down and have a heart to heart about how you're feeling and try to reach a solution.

A couple of potential ideas would be, everyone puts their phones on mute and leaves them in the center console until the car is parked at the destination. Yes I realize it could be seen as punishing the passengers, however it's also a compromise solution.

Get him to find a safe space to pull the fuck over to check his phone. Assuming you're in the USA or Canada, unless you live in an extremely rural area there's likely going to be somewhere to pull off the road within 25km / 15mi.

[DISCLAIMER - this third solution obviously require a healthy relationship and trust] A third possible solution would be to let the passenger check who's calling / who texted, and tell them how / what to respond. I'll do this when riding with my Mom, or Husband, people who I trust not to mess around with my phone. There's obviously people who I've driven with who I'd NEVER let use my phone.

Is there anyone you can car pool with to avoid riding with your Dad until he agrees to stop?

If all else fails you could send your local PD an anonymous tip about a drive texting and driving on the routes your Dad frequently drives. Yes I know this will be an unpopular opinion, but the reality is he's putting the lives of passers by in harms way.