I cannot for the life of me find what starting Resolve is! I assume you buy it with stat points. Am I correct? Also, is there a cap on how many can be spent on a roll? Thank you, Immortals!
Also, if a Wraith drains a stat, can you increase it without gear (including a blood rune)? I assume not and if I’m correct, screw Wraiths! 
Resolve is one of your stats. It starts at 1 unless you raise it when divvying out your points to build your character. You get a free point of Resolve for every session you survive. You also get resolve from the GM for doing awesome things. It replenishes to full on a roll of triple 6’s.
I haven’t seen anything that suggests a cap on how many you can spend on a roll other than your maximum total, so swing away!
Regarding wraiths there’s no definitive guidance, but this is what I would go with. It’s captured the character’s life essence, so if you destroy the wraith, I would assume the lost essence is regained the next time you rest. Likewise if an Immortal dies and returns to life, I would imagine they regain whatever points they lost as part of their regeneration.
I would also imagine there’s consumable remedies that can counter the drain, either some kind of high tech medicine that rebuilds the damaged flesh or a spellstone that mystically removes the curse.
But also Viking Death Squad is a grim game. If you want to deny any or all of these methods of restoring a maimed character it would not be out of keeping with the tone of the setting.
Thank you. I really dig the “kill the wraith and get back what was stolen”. A major impetus to finish it off, even if later. I’m also looking for ideas as to how Immortals return if their bodies have to get left behind (which may realistically happen with a 10-foot tall iron-clad giant!) As cool as a rescue mission is, that’s not always viable given the environment and enemies, plus losing a character for an amount of time sucks.
My thought is to just have them “spiritually bonded” to their squad. An almost subconscious thing that has them coalesce from the aether once they can (i.e. “when it’s safe). It’s magic, after all!
I’m very pleased to see how much non-combat depth has been put into a game called “Viking Death Squad” and the breadth of empty canvas to build on. Hank deserves a much higher place in the pantheon of designers who’ve made the hobby better!
I actually have a whole post on here mulling over different ideas to deal with that issue if you want to go read it. 
My personal choice in our game was to tweak death and regeneration and port in the ICRPG death rule: roll 1d6. If you’re human that’s how long folks have to stabilize you before you die. If you’re immortal that’s how long until you Deadpool yourself back together.
We also nixed the three total regenerations thing to a “unknown max where you die for good, but it’s different for every Immortal”. We also view “10 and 10 only” as the common knowledge of folks who don’t know about the surviving tombships, but that it’s not actually true. The truth is there’s 10 for now, with the promise of as many as can be found.