Storm, he's not talking Imbuing, he's talking UNRAVELING.
NOTHING is worth its modified imbue weight when unraveling.
As for the second group of questions
A. If it was SC with FC +1, yes - but those are mostly artifacts and I think theoretically, some ML crafted items.
B & D. Hit Mana Leech and Hit Life Leech have their DISPLAYED value modified by the final weapon speed after applying SSI, from a change about 3 or 4 years ago. The displayed value is what is used in the calculation of how much you leech. However, the intensity is the value before such modifications. Note that Stamina Leech has a max intensity on non-artifacts of 50%, but still functions the old way (and isn't modified by the swing speed)
This is why the soul seeker, which originally had a displayed 40% in all 3 leeches, has HML & HLL displayed as 32% (with the 40% for HSL unchanged). It has 80% intensity in all 3 leeches, but the weapon's base speed (the radiant scimitar is one of the faster weapons in the game) plus the 60% SSI (a 200% intensity, which of course can only be on event items and artifacts 60% SSI = a 1/2 second reduction in the time between swings) results in the modifier for the displayed amount being "Times 0.8"; 40%*0.8 = 32%
Ranged Weapons have a *0.5 modifier for displayed HML & HLL ONLY - this was meant as a form of balance, as without it, Repeating crossbows (and throwing weapons) with the properties would leech far more than most other weapons from sheer speed, and the other archery weapons would do so from sheer damage (as its slow speed would always put heavy crossbows at around the 100% mark).
IIRC = If I remember correctly. It's one of the most common and oldest acronyms on the internet. I remember having to ask what it meant - in 1995.
At NO point is getting 2 relic fragments guaranteed from unraveling an item. There's a CHANCE you might get 2 (maybe even 3) from unraveling a high-end item, but it's not guaranteed even for a gargoyle 120 imbuer at the the queen's soulforge. I believe the chance of getting multiples from one item goes up with skill, but it never gets remotely close to being a sure thing.
Imbuing lowers the final value for determining what you get from unraveling, by multiplying the value by 0.7 (not 1/2). So an item imbued with 5 100% properties would only unravel to enchanted essence, as the imbuing penalty reduces it to 350 Intensity.
On the other hand, Enhancement can raise the value of an item for unraveling (but not enough, anymore, to offset the penalty). OF course, you end up with a 30% or more chance of breaking the item, but it can be used to turn a percentage of items that fall just short of relics into ones that can be unraveled for relics.