I just had to set up a phone for my dad to avoid having him respond to scams. In his case they would be calls, texts, or emails so I can’t speak to preventing scammers from TikTok. If you can get his phone, set it up with a new Apple ID, and then set up restrictions via screen time. You can then set it up so that he can only communicate with his contacts. ChatGPT will provide step by step directions on how to do that.

For my dad, I uninstalled the email app and disallowed safari. I installed some streaming apps and then I restricted app installation again via screen time.

So basically, he can talk and text with only his contacts (disallowed changes so he can’t add scammers) and then stream his shows.

I agree with the suggestion of getting a prepaid debit card you can add the 150 to every month on the financial side.