Planning an Ultra on Elven Wizard

[Blasphemous]

Since I've already completed the game on multiple characters without save scumming, I would like to give ultra ending a try.

My chosen char is Grey Elven Wizard, since it's a relatively easy char for early game when using the bug temple as initial leveling ground - I safely get to lvl 12 or 13, get 50 HP, 150 PP and then off for a session of stairhopping in ID to get the necessary spellbooks (SoA, knock, some offensive spells, invis, tele, heal, maybe acid ball) and some initial gear.
I usually emerge with most of the desired spells at 500-1000 charges and Le & Ma stats anywhere between 25-30.

Now normally I have no problems doing all the surface and Thrundarr's quests, but the first real problem is saving Khelavaster.
I just can't seem to get a wish or find the amulet outright, and am either forced to forfeit his life or go for a grinding session and hope for random loot, but where?
ID? would have to descend to lvl 20 or 24 to match the danger level and even then randomly getting it is a tedious process.
DF is of course cleared, pools sipped (last three games I had not a single wish from a pool, despite finding at least 4 outside of DF).
Bug temple interior not yet touched, RotHK in my backpack, pyramid cleared, dwarven graveyard cleared, fire temple done.
This is usually when I'm supposed to go deeper into CoC. I don't have a char at this stage yet, but this is a typical line of progression for 99% of my wizards.
I also have 7LB at this point, usually from one of the vaults, I am of lawful alignment, around lvl 20, lots of holy water, deity is at extremely close but plenty of artifacts already found, mostly guaranteed ones, make me ineligible for precrowning.
Last char died after casting too many fireballs in the animated forest and subsequently getting vanquished by an uber tree.
One before that fell down some stairs in ID while very strained and broke a neck.
Yet another char met an early end when I accidentally meleed ogre king around DH2.

So all in all, my deaths usually result from my own carelessness and stupidity rather than the general RNG's maliciousness, and mostly in the early-to-mid game (there was one late game accident when SoA ended while I was doing w5 waiting for herbs to regrow and got crushed by luggage, a lesson I learned). But if I'm able to overcome them by being more patient and careful, I should be ok (as in the RNG doesn't seem to give a damn about me either way). I usually get 1-2 RoDS later in the game, around casino and greater vaults, as well as a wand of wishing, mostly around Blue Dragon Caves, but that happens in games when I actually let Khelly die and just move on for a normal gate closing.

I will roll another char soon and get to that stage when I have to save Khelly, then post a log.
As for the rest of the journey to ultra ending, I know the drill, I finished the game that way multiple times cheating but I want this one to be legit.

So, how do I get that damn amulet of life saving? Gremlin bomb is a viable option but rather tedious. Considering I don't care about real-life or game-time constraints and don't mind using some of the scummy techniques, what additional advises would you give me?