You need to read some books
Race car chassis - Design and construction by Forbes Aird is one I would recommend.
It's easy to read and has plenty of real world advice that you really need. This book will explain in layman's terms how you design a chassis (even a simple one) taking into account the loads that said chassis will experience.
After that maybe Tune to win by Carrol Smith. This book will help you understand the basics of suspension and steering systems.
Nothing you've done thus far is safe or functional. Harsh but true.
I mean even fundamental stuff, like you've welded the chassis with a gassless mig.
Gassless mig's do a shit weld to start with, then i bet every weld's been stop-start forming heaps of cold brittle point and undercuts, all nice stress concentration points. Then you're going to hard mount a
vibrating engine to the frame.
The flat, twin beam chassis has no real torsional stifness and will flex.
Between the flexy chassis and the engine vibrations the welds don't stand a chance.
You would have been better off making a chassis from wood and bolting it together.
That's not even touching your suspension design...
It's kind of a case of "you don't know what you don't know"
Take a week read two books, get learned and then do a proper job of it!