Nick is not being targeted for his background but rather because he was the last person to have been seen with her and admitted to supposedly driving her home.
Poindexter said that Nick did not work at the bar, I believe in an effort to distance himself from Nick. I believe that he was paying Nick under the table so there would be no official record of him being employed there. Other people that frequented the bar all believed that Nick worked there. Nick did have money, as IIRC, VOH said that they had seen him with money before. He had money for cigarettes and pool, food and had a car. What would be the sense in having a car if you could not afford to put gas in it every once in a while at least?
I don't believe that this crime was planned, but rather was something that happened because of poor impulse control, anger, rage, spur of the moment type thing. Nick already demonstrated his poor impulse control when he attacked the 5 year old little girl while he was at her home with her mother only being gone a short while.
I believe that Nick was more interested in Kelli, than Kelli was interested in Nick. He did admit asking about her marital status after all which I believe shows he was interest in her. His comment about her using her cell phone to text ALL night makes me feel that he was paying very close attention to everything that she did that night. Perhaps he thought it was a date, thus the reason for the unpaid bar tab in both his and Kelli's name and he became jealous of her attentions being elsewhere besides on him. Nick also raised my suspicions when he did not give any information on WHERE he picked her up that night, especially in light of all the other information he gave. Regardless of the state of her marriage to MB, I just don't think that MB was involved in her disappearance JMO. It may prove out later that I am wrong about Nick, but so far nothing has come to light to make me willing to let Nick off the hook for Kelli's disappearance.