Port tacking seems to be well addressed in Part 2 Section A – Right of
Way and Section B – General Limitations, and also seems to be addressed
in Section A. Plus the penalties for this type of infraction seems to
be defined in 44 PENALTIES FOR BREAKING RULES OF PART 2, and for other
simiar infractions in 31.2, 44.3, etc.

However, failing to sail the course might be more applicable in this
case. I guess that my question regarding rule 2 and the restricted line
is more related to failing to sail the course a proper manner and at the
same time doing so in a manner that clearly gives the violating boat an
unfair advantage.

Yes, as you point out, this is a violation of rule 28. Since it isn't part
2, you can only correct it by unwinding the string properly, not a 720 (or
other alternative penaly). Should he not fix the mistake, the only penalty
is DSQ.

What would be a violation of fair sailing is if it were something like the
last race of the series, all he needed was to push one boat back in the
fleet, intentionally violated a rule so he could get on top of this one
boat. A similar incident