I went for my first PPL lesson on my 41st birthday and got offered an airline job a few days after my 43rd birthday, so you are not even nearly too old!
I also had a full time job during atpl study but it was manageable. Because I was older, I wanted to get everything done ASAP for fear of being too old to be hired. I did the ATPLs in 3 sittings over 6 months. It can be done, but it's an almighty slog. If you have a partner or kids, you really need them to support you by giving you the space and time to study everyday.
My advice is hit the banks and hit them hard. If you get stuck on understanding something, search the topic on YouTube. I made the mistake of reading through the theory books before starting the bank, and in retrospect that was a waste of time. In my opinion, everything you need to get a 90% average can be found in Aviation Exam or more recently ATPLGS.
Best of luck to you.