I'll better split this into two posts. My solutions:

First problem: Use ssh-agent to store the key.

Second problem: I have several scripts that start tmux sessions with every necessary program running. There are tools like tmuxinator to make the creation of presets easier. I run my own solution though as I need the flexibility.

Third problem: Something like Travis CI?

Fourth problem: Taking a look at all the shims, frameworks and helpers helped me get a general idea of what works and what doesn't on certain IE versions. I wouldn't worry much about the inbetweeners (IE7, IE9). Windows XP is the biggest reason why people use IE8 and if you're targeting that market it would be best to invest in a workflow that minimizes the differences and get as much knowledge about the lacking features of IE8 as possible.