You are not too old, nor too large but some of the above points are very good. Let’s not sugar coat this it’s not an easy path. Firstly how much research have you done into a career in flying, hopefully a lot, if not here are some points to consider.
Taking a loan to learn means you will pay a lot more to learn to fly. A debt that you will then need to pay back. Initially you will need to gain experience in GA (unless doing an airline Cadetship) which at entry level will pay between $20000-$40000. Can you and your young family live on that whilst possibly relocating. “My wife works” I hear people say, great but how flexible is that job around your constantly rotating hours and children’s schooling? Most airlines need minimum of 500 hours but realistically need 1500-2000 hours in a competitive market (which it still is), how do you plan to get these? What will the industry look like when you do? What is plan B if you’ve spent this money and don’t get an airline job?
Are you you and your family prepared for what it will do to your family life? Will your family resent all the time you may be away, birthdays missed, Christmas missed. If you go the long haul route wil they be happy whilst your away for 7-10 days having drinks and exploring the world whilst they are at home?
Getting a class 1 Medical is the first step. CASA will need all the usual tests, but if you’re a bigger person with a high BMI you may also need to do a sleep study to look for sleep apnea (CASA is very fond of this at the moment).
It is worth looking at all the angles and outcomes, go speak to many flying schools big and small, don’t just accept the shiny brochures with pictures of jets that some schools show you. Ask questions, lots of them! It can be a great a rewarding career, but many stumble along the way, go in with your eyes wide open.