Q:

If a living person had been inside Starman's suit, would the launch have been survivable?

The spacesuit in the falcon heavy test launch was a genuine test article. Assuming the suit performed nominally could a person have ridden the roadster into space?

A:

If the suit had been connected to a suitable life support system, the rider would very likely have been ok during the ascent, because:

The car appeared undamaged.
The suit appeared undamaged.
Racecar drivers routinely experience on the order of 5 Gs in similar seats, (albeit for seconds at a time, not minutes). Adding the car AOA to the seat inclination it looks like Starman is leaning back by maybe 60 degrees. Good though not ideal. A G-suit would be nice.
The faring is only jettisoned when the residual aerodynamic forces are tiny.

Depending on the helmet, there could be an acoustic problem early on. The F9 user guide puts the sound level at (around) 130dB; the FH is likely louder...

