I don't think dropping to 300 or any number > than 250 make any differences to you; people at that level won't see you with more than 250 mobs. Just keep that mob. It's better if you have 499 mobs, people won't attack you because of Thug Life missions.
To play with explosives is like playing with fire, you may got burned by your own fire. Your income is just 6K/hour & your atk/def is low, you might waste too much for explosives but no benefit at all. Imagine you rob 2k from a building but lost 16k for explosives, what gain ?