Yes, I think you should definetely back off the intensity. Decrease total volume, frequency of workouts.
I like to do my first lift to failure, and then just back off on the other exercises.
I think people who are tall and skinny need CARBS. They focus so much on protein, but they need a much higher carb intake.
From my experience, a natural will not see any benefits from eating over 1.25g of protein per lb of bw.
A client and good friend of mine use to weigh about 155 lbs at 6'1.(up from 135 after 6 months of training) He was ripped with a good six pack. After another 6 months he was still stuck at 155lbs despite eating well over 350g of protein a day. When I analysed what he ate, I realised that he was lucky to get 250g of carbs a day. We backed off the protein to roughly 200g a day, from food only, and increased carbs to 600g.
4 months later, he was 185 still with a six pack. Today he's roughly 195lbs, still natural and he still consumes only 200g of protein a day.