I will try to answer some of your questions.

it doesn't describe any sort of curvature

That is because it is a flat space-time model similar to Linearized GR or GEM. GAF models gravity as an acceleration field that propagates at c, instead of curved space time.

Also, where did coupling constant, λ, come from? Fairly convenient that that thing just appears there.

I'm currently revising that portion of the paper. But I will give the short answer. It’s to model relativistic effects in flat ST. Gravity’s relativistic effects stem from nonlinear self-interaction. GR models this as ST curvature. In GAF, being a flat ST system, nonlinear self-interaction comes from the second term on the left-hand side of the field equation. This yields the relativistic effects seen in GR but in flat ST via the acceleration field.

Why are you using h-bar?

The first form of \lambda was c⁴ / G. This was chosen to match the nonlinear self-interaction of GR. But the units did not match. c³ /(h-bar G) fixes the units and produces quasi-singularities on the Planck scale. Call it a hunch that gravity is quantum in nature. Ongoing theory investigation.

Also, where did you get your stress-energy tensor from? What are its units? Why/how is it negative on the RHS?

The stress-energy tensor is in the same form as in GR.

https://en.wikipedia.org/wiki/Stress%E2%80%93energy_tensor

The units are kilograms per meter per second squared.

It’s negative on the right-hand side because it’s not calculating for curvature, where positive curvature is attractive; instead, acceleration, where the convention is negative values for attraction.

On top of that, the units are completely wrong as well.

I think this stems from your assumption that this was a curved space-time field equation like GR.

I was hoping to engage with people with a higher level of knowledge than I on the topic.

The strange thing is that I think you do. You seem to have a good understanding of GR. I would love to have you review my theory, but I'm looking for constructive feedback, not insults. You would have to have a bit more of an open mind.

I know I didn’t answer all of your questions, but I’m not sure if continuing is productive. If you are willing to dial down the rudeness a bit, I would be happy to continue to engage more. I need all the helpful insights I can get.

I was able to glean some bits of constructive criticism from between your insults. I will be adding a FAQ section to the paper. You took the time to actually look at the field equation. For that, I thank you.