You're probably in line with the rule book. But in general when designing structural things, just picture where the loads go for various cases. You don't need to do analysis, just stare at it and think for a while.
Ex: If there is a 20 G crash, then there will be ~3000 lb ~= 13kN pulling forward on the bar. If you triangulated the shoulder harness bar nodes then this would be borne in tension or compression to other nodes around the frame, but it's not, so all this force goes into bending the main roll hoop. You could use something like this to do some hand calculations:
https://www.google.com/search?q=simp...90%3B798%3B474
I guess my point was to ask why you have so much triangulation everywhere else but not here? What's the justification for triangulating everything else with such heavy tubes but not one of the safety-critical nodes? I assume that most of your "extra" nodes are for triangulating some suspension bracket or something. If I were you I would work on combining these together / using the "rule-required" nodes for these and eliminating excessive tubes.
As for tube sizes, I'm pretty sure no teams that I know of go up in wall thickness to get tube manufacturing tolerance against the rule-spec'd wall thicknesses. Are your tubes actually that far out of tolerance? 10% is a lot, I'd expect wall thicknesses to be within 3% and for that to be acceptable at inspection. In my experience 4130 tubing from the German mills (Benteler, etc.) always satisfies this.