The root of the problem is two fold, as I see it. First you let her control the budget. You have mentioned before that you are ADD and let the finances get out of control, but that isn’t really an excuse. You can manage the expenses if you want to, though it does take some effort. Take control of your finances, do it responsibly, and she won’t have room to question how you spend your money. You do need to show self discipline and an improving financial position. You can do this.
The other aspect is that your wife is a control freak, for her own FOO reasons, whether good, bad or otherwise. You also know her need to control is a reaction to control her feelings of panic. She needs to learn to reprogram these reactions, and how to do that is the real question. Confronting her is part of the approach, but soothing her is also critical. I think Fearless made a good summary of what your wife might be feeling.
She let slip out that you should buy her something, and that is probably the truth about what she feels even though she deflected that to focus on the kid’s needs. Underneath all that control is really a need for compassion. But once she gets it, she feels uncomfortable so she throws it back in your face. Maybe get her something small to make her feel wanted, to show her you are sharing a gift with her of the fruits of your labor. I think she might be feeling a little abandoned, so go on the trip but give her the validation she seems to need. But don’t cancel the trip. I agree with the others that doing so will set you backward. (BTW, what is that second job? Are you jobbing out as a gigolo on the weekends? LOL!!)