In my experience, the Hardness to UTS correlation is pretty good for low-alloy steels.
The Yield Strength can be estimated if you know the Yield to Tensile Ratio. For Quenched and Tempered steels, this can range from around 75% to 95%, depending on composition and heat treatment. For 4130 in the Q&T condition, in thin enough section size that you can safely assume >85% martensite formation on quenching, at 30-35 HRC I'd expect a Y/T Ratio to be around 90%. For thicker sections and/or lower amounts of martensite fromed on quenching, it could be in the 75%-80% range, maybe even less.
All that said, for 30-35 HRC, I'd expect UTS to be 140-160 KSI. With a "good" quench and temper, you could expect the YS to be 125-145 KSI. With less than "good", the yield strength could be in the 100-110 KSI range
rp