I would argue that while Lucas is sensitive, he is emotionally distant from others. He cares but he struggles to empathize with people and sometimes doesn't understand the weight of what he says. He's also a person who is very vulnerable to stress and often lashes out because of it. A big part of Lucas' character is that he doesn't actively seek help. In his route, Wallace is basically forced to be the proactive one in order to push Lucas into a safer environment for him both mentally and emotionally. You're definitely correct on his self-esteem though, he's dealing with some intense self-loathing and often regards himself as below those he deems as good people like Aure and Wallace.
Hmmm. I would agree with what u say no doubt. When. I got to the give space or admit feelings i thought it would be best to admit feelings but i had to know the other answer first. I cried to the bad end. For like 15 to 20 min it was very sad. I originally admitted feelings and was happy with what went forth after i did some really heartwarming moments.