The project is a high pressure test system
The controller will also need to take into account various fault conditions and respond appropriately
But the way you talk, are these Arduino's not very reliable?
Is it a wrong design choice to go with these due to problems with them?
* Should I fuss with interrupts? Or should I just write one big loop that goes on until power is shut off? I could, for instance, tie my switch changes to interrupt pins...
* Should I store data on my system layout and write simplified code that processes this data, or should I hard code it all into instruction memory?
* How should I handle memory and instruction memory faults? I need to understand the possible failure modes and be able to address them with additional components.
Not thst the serial transmission to the PC is blocking; this has to be carefully examined by you.