Current Training Process

I apologize in advance for this post. The grammar may be a bit messy and the overall form of it won't be in any format. First off just to clue you in on my body type, I'm 6'4'' and 177lbs, this is what I'm working with. This is a current training regiment I use, not as often as I should, when I train my body. Usually I start off with warm-up exercises, push-ups, pyramid push-ups, sit-ups, crunches, etc. Anything that is simple and does not require outside sources (aside from a floor or occasionally a chair for roman-chair sit-ups) to warm the muscles, build them a bit, and get the blood flowing. The next step I move onto varies by my mood. Now bear with me because this is a bit strange. If I'm upset or aggravated I usually work my 100lb punching bag. I start off with arms (straight jabs one hundred count, hook jabs one hundred count, palm strikes one hundred count) then move onto legs (snap kicks one hundred count, crescent kicks one hundred count, rising knees one hundred count, high kicks fifty count, stepping side kicks fifty count) and finally at the end I do mix combination's and try to see what motions work better together and what can be used but only if done properly. If I'm happy or just apathetic I lift weights. For my arms I use a single dumbbell (due to money issues I only have one) ranging from twenty-five to thirty-five pounds. I do curls (ten to fifteen repetitions), shoulder lifts (to fifteen repetitions), side lifts (fifteen to twenty repetitions), arm raises (ten to fifteen repetitions). For my legs I stick mostly to stretching and unassisted squats (fifty to eighty repetitions). So far my results have been varied. I noticed a massive strength gain in my arms recently from the curls and the push-ups. My legs have been tightening up significantly (there is still a little fat around the inner thighs and the buttocks but the squats seem to be effective along with the kicking exercises). My one draw back and upsetting footnote would be my chest and stomach. I can't seem to tighten them up or create definition. I'll admit my dietary habits are not the superb but I do not eat fast food anymore and I try to only eat one meal a day. The sit-ups seem to not have much effect and when I do have the opportunity to use a bench press no matter what style I do (less weight increased reps or more weight less reps) I see no change. I'm still a little flabby and it bothers me. I'm trying though and I guess that's all I can do. Any advice or suggestions out there for those of you who went through the same problem?