I am in a similar position to yourself although I am a year younger than you. I also work 3.5 days a week. My trade is a Lorry Driver so I do end up with a lot of sitting around waiting to be loaded which is excellent time to be brushing up with Theory etc. I am flying 2-3 times a week as long as weather is okay.
I am doing dual modular and you can easily do it for 50k all in. As you already have 12k I would find a local field to do you PPL and then do your ATPL theory. You should be able to do it with that 12k you have saved. The great expense comes after that with the ratings but doing your PPL and ATPL theory you are already the vast majority of the way there. Then you need to try and find the remaining 40k. Whether that be taking equity out of your house or securing a loan. First thing I would do though is your Class 1 medical.