Whether the cost of the item has gone up or down since the time of preorder, the price you locked in at the time of preorder will be unaffected
See rule 605, Mana Abilities. The activation of Llanowar Elves' mana ability will trigger Leyline of Abundance
Once you have your prices locked in and your stack sorted, you can dive deeper into how to sell Pokmon cards and pick the selling strategy that fits you best
Besides, if your board state is poor and you're taking damage, gaining 7 life will not buy your much time, and your opponent's heavy-hitting creatures are still there
You can build K'rrik pretty much however you want, but unless you're playing pure jank, this Commander probably only belongs at tables playing Bracket 3 or higher
Whatever direction you take The Mycotyrant, whether it's crusty old Fungus cards from nearly 20 years ago, a highly tuned combo deck loaded up with tutors or something in between, I hope if you build around this card you're able to get it to do what you want