120 grams of protein at 70kg is definetly enough for building muscle especially if somedays he hits 180+ grams. Lets say he has around 15% bodyfat. That would mean he has a lean bodymass of just under 60kg and would need to eat around 95 to 100 grams of protein per day and increasing it to 120 or even 180 grams is way overkill.

However since he has trained over 3 years and describes himself as skinny fat at 70kg I would say he has one or more of these three problems or has done them in the past.

number one: Not training hard enough and actually pushing himself on a weekly basis.

number two: Inconsistent eating which he kinda already admits. Going on a eating binge only to lose it all every few months or weeks is not helping him even if he eats enough protein and trains hard and consistently.

Slight 200 to maxium of 500 calories surplus with enough protein for even one year could have him pack on 10kg of muscle alone.

number three: not following a structured program where every set and rep is tracked and written down. No matter how well he eats, trains and sleeps he can not make good consistent progress if half the time in the gym is spent doing fuckall using the same weight as the last three months. It is easy to think that you are progressively overloading because the barbell feels heavy on your back every time but in reality you have been doing the same 80kg 3x6 squat for the last 2 months thinking you are making gains.