I always found that doing all my cutting in the 12 hours leading up to a weigh-in was best. I should emphasize that this is 12 hours before the weigh-in, not the competition. Any further out feels like torture. The amount depends on you and your size but I was most comfotable with staying within 10lbs of my target weight. I've known guys that could go higher though. The weight you will lose in that 12 hours will all be water weight so it will be important to put that back on after the weigh-in in the form of a sports drink or water and electrolyte supplements. You should only eat enough to be comfortable. Don't stuff yourself.
"One of the workouts I do for conditioning consists of 5 dead hang pull ups, 10 med ball slams, 15 burpees and then 25 jumping jacks (as a circuit x 10 to be completed in under 20 minutes)."
I'm sure this makes you tired and sweaty, but at what point in a boxing match do you have to do any of these things?
Now, when it comes to additional bodyweight accumulated through barbell training, you have to consider that the majority of gym-goers are accustomed to seeing big guys who are in terrible shape. How often do you see a gigantic meathead sweating his ass off and sounding like he is drowning while walking on a treadmill?
Most of us see it all the time, however, there is a way to accumulate muscular bodyweight without appreciably increasing strength, and in turn, the ability to do work. We tend to refer to this method as "bodybuilding". The Novice Program increases strength, whereas the bodyweight increase is going to be based on how much you eat. It is possible, though not in the least bit optimal, to increase your strength rather profoundly without an appreciable increase in your bodyweight through doing the program.
Now going back to your training and where it translates to what is encountered during a boxing match, surely you could appreciate where a more muscular, thicker trunk achieved through heavy squatting and deadlifting would be helpful. Also, increased strength through the full range of motion on the squats will increase your ability to apply force to the ground which will make you faster and quicker, and increasing your power production through power cleans and strength in the hips through squatting will make your punching power increase by increasing the amount of power that can be produced through rotation of the hips and trunk.