Weads, I think you have been given the answers above.
Basic effects of controls sortie on a turbine helicopter shows raising the lever increases Ng and ToT and lowering the lever does the opposite.
You are unlikely to exceed an Ng limit because that will be set in the FCU with bleed valves to dump fuel pressure. You can easily overtemp an engine without exceeding Ng limits.
Most aircraft I have flown don't have a PTIT/ITT limiter so it is the one thing you have to keep an eye on. More modern aircraft may use a Power Index (PI) to show that you are near a limit without specifying which one.
Cooling the engine is critical so whilst the fuel flow/Ng/ITT relationship might be linear, or close to it, the cooling effect of even a reduced amount of air may well not be linear.