Okay so I ended up asking the design team (I just wasn't aware of how to to it before) and I´m glad to share the clarification in regards to Deathlace.
1- The Dark Elves do not need to be involved at the matchup where the tackle is happening.
"[…] Deathlace can be used to modify the dice of managers even at match ups where the Dark Elves are not present. That is why it says "any manager""
2- Deathlace is resolved based on the final dice result.
"[…] the intent is for Deathlace to occur after the final dice result. That would thus include any other modifications to the roll, like Dodge."
3- Deathlace can be played anytime during the tackling sequence following the player turn order (first player then clockwise order) BUT its resolution - as opposed to announcing Deathlace is being played - occurs according to point #2 above.
"Yes, according to the rules structure, I suppose it is possible to declare Deathlace before using Dodge but not use its effect until after using Dodge."
It means that if I play after the tackling team but before the tackled team then I can make use of Deathlace before the tackled team attempts to Dodge.
4- Two "BOOM" symbols on the final tackle result with Deathlace involved implies the player is both downed and injured.
"two "target down" results rolled in conjunction with the Deathlace ability would result in the tackled player being downed and then injured"
Some further clarification was then provided about upgrades in general:
"I also would like to point out that when Team Upgrade abilities (like Deathlace) conflict with other abilities occurring during the same phase (like Dodge), managers should resolve them in turn order starting with the manager who currently holds the golden coin. So if one manager wanted to use Dodge and another wanted to use Deathlace, the manager highest in turn order (closest to the manager with the golden coin) would use theirs first. Then, the other manager would have the opportunity to reroll again using his ability"
It's quite interesting because it means I can also "pass" my turn and not use Deathlace and let Dodge happen, then announce Deathlace. That's probably what I would do anyway since I wouldn't waste it on bad tackling roll (final result), I need to know what comes after Dodge I guess.