I tried dev.dangerousprototypes.com and the shop link goes to something without pcbs or sla printing as an option. Some of the merchandise has changed price, and I think there are some new things as well.
ARM documentation is available on arm.com. The instruction sets are mostly upward compatable, but some features are optional. The instruction sets on Cortex-M4 processors should be the same (modulo optional fetaturs) but the peripherals will diiffer.
Look for "mr16" led drivers on ebay, dealextreame, or other china electronics source. The rectifier diodes may be bypassed to reduce voltage drop, and dimming may be set with a resistor or pwm source. I've gotten 10 for less than $2 on ebay.
LiFePO4 batteries are lower voltage than other Lithium ions, you should never let them get more than 3.8 volts under charge (3.5 is better) and 3.0 is a reasonable fully discharged cutoff. If you treat them well you should expect much longer life than other Lions.
When I was doing my first project in Kicad, I've found problems with the layouts in the dangerous prototypes library.
Various TO-220 have the pins numbered 132 rather than 123. This means when you use them with transistors from other libraries the signals will be routed to the wrong pins. I wound up using an outline with a heatsink to avoid this problem, but this wastes board space since I won't be using a heatsink. They may also have the problem mentioned below.
The dp_devices-TO-92 has solder mask over the solder-side pads. LED-5MM also has this problem.
As some of you may have noticed, I'm not as quick on my projects as some other people. I've got the parts (mostly from ebay) and the PC boards (with errors and quirks, so I won't share) and should be assembling soon. Not shown in the schematic is the fuse, I'm using inline fuse holders. URL below is for the kikad schematic.