Newbie.. is there a fix for this Sharp SQ-46P?

[obsolete man]

https://www.radiomuseum.org/r/sharp_sq_46dsq46.html. I believe that is the tv I have, although mine is a P at the end, not a D.

Here is a video sample of the picture issues: https://youtu.be/kq9vkrIIh1A
Another sample: https://youtu.be/NRbsyMHtNm8

Base on the picture, the snow, the lightning effect, etc. Do you see any telltale sign of anything that we can pinpoint?

Set-up is a fire stick to HDMI to RCA adapter to RF Modulator to 75/300 ohm adapter to the two terminals on the tv's VHF. I have another TV in the same era, late 70's Zenith, that's producing a clear crisp picture under the same set-up. But I just can't focus this Sharp. Here is the Zenith with a great picture under the same set-up: https://youtu.be/rxd6hPlz4Kc

Do you guys think better video delivery equipment would help? Or, will the Sharp TV need surgery, as in opening it up. LOL! I don't have technical knowledge, or even know much lingo about these things. I just started getting old tvs out of nostalgia. So if you advise me, please talk to me like I'm a 5 yr old. LOL!

I've asked for help in other forums too, but I see videokarma at the top of search engines, so I figure I'd ask for help here too to gather as much knowledge as possible. Thank you for your time.