That being said, I look forward to be independent some day and try to spend my free time building something on the side. The problem is that it is not not as easy as some people make it seem. Depending on how the day at work was, I might be completely exhausted mentally and not in a position to do anything in the evening.
This part-time approach might not work for the OP as the job already seems to be stressful. Given that he has a cushion, is probably quite competent AND hates the current job - in his position - I would quit and do something that drives me.
Make a time bound plan with milestones that keep you on track and evaluate after a year or two. If it does not work out, you can always come back to the industry with your current experience and whatever new you learn starting up.
Would you get the same package or better? Maybe. Maybe not. But you can look ahead knowing that you tried. Then you get back to the job till it gets tiring again, or you get the bug of going out and doing something else again. :)