Nice work on changing your body composition. It sounds like you are off to a great start.
Like you, I'm pretty lanky, too (6'1", 160) and have been that way for most of my life. I'm 31 now, and only recently have I started working to bulk up a little. Last spring I put on 10 pounds to reach 160, and sometime this fall I might try to bulk up a little more to reach 170.
The paleo diet should allow you to get adequate protein to build lean mass. If I were you I would consider adding a 3rd or 4th LHT day to each week while you are trying to build up your lean mass. You don't have to do that all the time. Once you've got the mass, it is easy to keep it. I found that out when I broke my hand in the late spring. I only lost a couple pounds despite not being able to lift heavy things.
When you are making a push for some gains, you might also want to dial up your food around your workouts. Make sure you get extra protein in your system before and after workouts and maybe add some excellent carbs like a sweet potato to your post workout snack.
Some of my all time favorite articles on exercise are from Dan John. He helped me with building some muscle by pointing out I should focus really hard on that for short periods of time. For a while I fell into the trap of always trying to eat enough and gain a pound or two. That is hard psychologically. I love his idea of taking a 4 to 6 week period, hitting the gym extra hard and eating more. Then see what you got and go back to cruise control.