The 5602 heat sensors don't draw any power. They have a switch contact, just like a window sensor, that closes when the high temperature condition is detected. The specs on the 5602 are just telling you how much voltage and current the contact itself can handle. But those numbers don't factor in to your current draw calculation at all.
Similarly, the window and door sensors don't draw any power as far as the current draw calculation goes.
If you are willing to add the zone expanders, it's nice to have a single sensor per zone, or a group of sensors, such as windows in a single room, per zone. That makes isolating problems and zone violations much easier to track down.
Adding 2 M1XINs at 65mA each will put you just over the 1A limit of the M1's power supply.
I didn't see an M1XEP in your list. Are you planning on having one on your system? It's not required, but it makes configuration of the M1 much more convenient vs using a RS232 connection. But it adds another 300mA to the current draw calculation. Though you could power it with the included wall wart if you don't need to use the ethernet connection during a power outage.
There are several options for an aux power supply.
Elk offers several options with 1A, 2A and 4A outputs. Altronix also has many good models. I like the
Altronix AL400ULPD8, which is a 4A supply. It's more than you may need right now, but allows room for growth. You can often find these on eBay for less than list price.