Convertible car seats!! Which one should I buy? The one I currently have is not secure AT ALL!!!

So we have a safety first car seat, but it moves way to much. For side to side, we have to literally ram out rear seat back to secure the seat more, but it’s raised a bit off the bottom of the seat. The straps seem to tighten on their own? Idk. It’s just a no no! Anyone else experience this with safety first?

It honestly freaks me out. I want a new one TODAY. My husband didn’t believe me that car seats should be more secure than ours is. He just says he can’t see it being more secure because he can’t get our car seat to be secure. After I showed him 3 videos of car seats installed and where the don’t move...he finally believes me.

My question is...

What car seats do you recommend? And why? I’m so nervous of the same thing happening again.