1.- Yes, sure. You always must attend the EMC performance of your electronics design.
EMC or Signal Integrity, we are talking about the same. Although probably It's a hobbyist-project and you won't need to pass an emission or immunity EMC test in a EMC Lab but EMC is also the noise, the crosstalk or ground bounce and this could be a problem inside your project.
So, yes. For emission you can check: (only a summary)
- Raise/Fall Time in high speed signals.
- Layout of high speed. (Changes of layers, loop current...)
- Possible antennas. (Your connector and your cables could work as an antennas)
2.- It would better if you explain us more about your circuit.
I suppose there is a component that works as a switch. The out of this component we can call it "switch node". In this node the voltage is
$$V = L (di/dt) $$
; V is voltage, L the inductance of the node, i is the current, and $$di/dt$$ is the rise time (or fall time) of change.
This parameter is really important!
Maybe you can:
- Decrease the rise time. (Could it work slower?)
- Decrease the voltage (Could you use a lower voltage?)
- Decrease the inductance in your switch node.
- Include a snubber (a circuit for absorb the voltage peak).
3.- This question is the similar to 2 isn't it?