Let's start with your height. If you follow the standard Body mass Index 145 lbs or 66kg for 5'8 is still a bit under weight.But most bodybuilders don't follow a standard BMI coz those are only for average people who don't do bodybuilding.
It really depends on your goal.Since you want a medium ripped body with a good amount of muscle,you still need to bulk up.Just monitor your calorie by knowing your body.Because belly fats are excess calories that aren't consumed as energy aside from fats that you get from foods.
You can try different approach. get your TDEE to monitor your calorie if you are really concerned of getting fat. Use an IF calculator that can be found in the net,and it will give you an idea on how much fats,carbs and protein you need to consume.Ideally a more common approach is, more carbs less fats on workout days while more fats and less carbs on rest days.And you should always be high in protein daily. But it doesn't mean that you can eat a lot of fatty foods or eat tons of rice.Just balance them with great amount of protein foods (chicken breast,beef,fish,peanuts egg whites), fruits (like apples,pears,raspberries and banana) and more importantly green vegetables (broccoli, lettuce, cabbage and beans.)
http://www.1percentedge.com/ifcalc/I'm currently on cutting phase from 165 lbs down to 143 lbs at 5'6 since I focus more on ripping down to 15% body fat.
BUt unfortunately,genetics isn't on my side.Since I'm between meso and endo,I can't harness a full 6 pack abs.That's the reality.Genetics really play a major role in bodybuilding.Mesomorphs are lucky since they can cut body fat easily with ripped medium sized muscles or bulk up easily as well.As for ectomorphs, they can easily get lean but is hard to put on weight to get bigger.
As for avoiding pain on your forearms,try assistance exercise by doing light palm down and up wrist curls. Better yet take some fish oil.Best for nerve and joints.
Just don't overtrain.Because that's the common mistake that most people do in the gym. 1 to 1 and a half hour is enough per day during training.