I'll try to answer.
1) The "M-bug" is effectively the normalized bundle-hash containing the character M.
More information about it here:
Why is the normalized hash considered insecure when containing the char 'M'
2) Proof-of-Work was implemented in VHDL between 26th April '18 and 26th Aug '18 and became the PiDiver: https://github.com/shufps/...
1) In mid 2017 the M-Bug was found and the work-around for it is (inoficially) called "Mini-PoW". It could happen that a Bundle-Hash contained "M" which exposed a private key (and all following keys) directly and weakened signatures significantly. The Workaround simply recreates bundle-hashs until no "M" is contained within the hash. This is a brute-force ...
As stated in the instructions, you should run the installation as root by becoming root (sudo su), else it doesn't get the correct ENVs for root.
The correct link for the most up-to-date documentation is https://iri-playbook.readthedocs.io/en/feat-docker/getting-started-quickly.html
Note that the command only has one <, i.e.:
bash <(curl -s https://...
Disclaimer: I am not a developer
Have you tried following this tutorial?
Comparing the code might help.