Forget foehammer for a moment.
Let us forget Foehammer and the is it isn't it? circle. It is ambiguous enough that either side could be right. When the FAQ is written the "winners" will do a jig and say "I told you so, I told you so, I am so clever you should have listened to me because I am so clever, wasn't it obvious?". We are supposed to be mates, right? That was not supposed to be rude but I think we are getting carried away.
Anyway.
If someone survives a TH hit, they are reduced to i1 until the end of next player's turn. This IS clear even if it was not intended, as in for them to be picked out by a nifty shooting attack.
JotWW will remove them against an i1 dice roll.
The wound allocation is clear even if it is silly.
SCENARIO 1:
3 normal wounds + 2 PW wounds against 4 bolter marines and 1 flamer marine. 2 marines die & 3 saving throws are taken.
4 normal wounds + 2 PW wounds against 4 bolter marines and 1 flamer marine. The flamer marine dies "twice" and the 4 saving throws are taken.
It is clear even if it is silly.
TH explicitly lower i to 1. This is not ambiguous, even if you don't like it or it was not intended.
Preferred enemy usage is clear even if it is silly.
SCENARIO 2:
In cc each model attacks whole-heartedly with all attacks. Even if they will kill the Firewarriors and be drilled by the Tau gunline next turn. The intention is no pulling punches for your benefit.
Preferred enemy allows the attacker to re-roll to hit dice. Hits can be re-rolled. The Tau can be killed more slowly by accepting misses and taking re-rolls on the hits. This was not the intention but it is clear it is legitimate.
The preferred enemy usage is not ambiguous, even if you don't like it or it was not intended.