Is crew G tolerance modeled?

The answer is, of course, YES.
My standard issue methane tanker ("Sleipnir" class) has two separate sets of engines to address that - you can shut one off when nearly empty to reduce manoeuvrability.
Not only that, rapid spins can also kill the crew and their effect depends on where the CM is located relative to centre of gravity (that's why my ships have centrally located CMs even though it increases the probability of total crew kill by incoming fire).
Sometimes it takes rather special circumstances to kill the crew, and, of course, the main problem when combining all-or-nothing armour (especially when crew is placed in small armoured nosecone) with large propellant tanks is that thinly armoured tanks will get penetrated, penetrated tanks will vent and large tanks venting typically impart a lot of torque on the ship, spinning it up rapidly and turning the crew into jelly.