There are no adjacent lands to add Blight to, so Blight does not cascade.
Push can't Push anything (unless you can Push to a land 2 away - eg, Many Minds Move as One - and there's a land 2 away, see below).
Whether you can target the land depends on whether you can measure Range from your Presence to it. If you made a disjoint land via Cast Down into the Briny Deep + Absolute Stasis, yes, because the land is Range 2 from other lands. But if you completely wall off a land via Repeats of Absolute Stasis, then there's no way to measure Range to it, so the only way to target Powers there would be to either have Presence in the land or the ability to ignore range (eg, Finder of Paths Unseen).
Note that Isolate is NOT usually sufficient to generate any of these situations, since it only affects adjacency for Invader pieces (JE rules, p. 10). Tags: Island Boards, Push, Range, Targeting, 2 more...
Similarly if you move a piece inland, you move it further away from the Ocean: each land it moves through must be further from (any) Ocean than the one it left.
All game notions of "closer" and "further" use Range – you never need a ruler, and a land that looks physically closer might not actually be at shorter Range! (Discussion elsewhere) Tags: Range, Move, Sweep into the Sea
If a Range boost only increases the Range for a single Action (e.g., the Reach Aspect ignoring Range), then the farther-afield Dahan only grant Defend for one action of your choice (usually a single Ravage in one land). Tags: Range, Range Boosts, Bargains of Power and Protection, Reaching Grasp, 7 more...
All other targeting requirements still apply. This includes source restrictions, so if, e.g., a Power must be targeted from a Sacred Site and you have none, Shadows of the Dahan won't let you use it, or if it needs to be targeted from a Jungle, you need Presence in a Jungle to use it. The same applies for target restrictions other than Range, like lands with Invaders, unblighted lands, or restrictions on the target terrain; these must also be obeyed. (Discussion elsewhere) Tags: Range, Targeting, Shadows of the Dahan (Shadows Flicker Like Flame), Finder of Paths Unseen, 3 more...
Do Range buffs apply to Powers that affect "a land with your Presence" or "one of your lands"?
No. "A land with your Presence" specifies a requirement for the land you're affecting (similar to, eg, "a land with Dahan" or "a land with Blight"), not a numeric Range. While it is usually the same in practice as "a land at Range 0", when using effects that modify Range the distinction matters.
For powers like Punish Those Who Trespass or Firestorm that have a base effect with normal range and a further effect referring to "lands where you have presence", the range on the base effect can be extended, but the further part cannot.
For instance, if you reach all the thresholds of Punish Those Who Trespass and have extended range, you can use the base effect to deal damage in a distant land and use the further part to deal damage where you have presence (without extension). (Discussion elsewhere) Tags: Range, Presence, Targeting, Reaching Grasp, 10 more...
This is usually irrelevant, but can occasionally be important (for, e.g., Scream Disease Into the Wind, or other "after using a power on a land..." effects.)
It does not need to actually do something, as long as it has an instruction that could in theory modify the game state. Setting up a triggered action for the current Power only (eg: Lure's first innate) doesn't count, either; it's effectively an internal modifier as well, despite using a trigger for timing. Tags: Targeting, Resolving Powers, Range Boosts, Range, 4 more...
