I may sound like a complete d-bag for saying this, but Wilderness Medicine is not a fellowship. It's for EM docs who like the outdoors and don't want to pay off their loan debt. You should not pursue this fellowship, IMO, barring some very rare/specific circumstances that I can't even think of.
Palliative care pays.
Critical care pays.
Toxicology pays.
Pain pays. But you have to do pain. Shoot me now.
EMS doesn't really pay well at all (much of it is volunteer depending on the agency). Lots of EMS is government work, so even the positions that do pay, they come with all the crap that involves being a government employee, and very little money, and likely years of paying your dues working for free. I'm starting EMS fellowship this summer, and with the exception of possibly being more competitive for academic positions which don't pay much to begin with, nobody at any community shop will likely care about my additional training. It's more for me.
Regardless, if anyone is going to pay you for doing anything, doing additional training in said area is beneficial. For EMS, the age of non fellowship trained medical directors is likely coming to an end, and the expectation for new jobs is that people complete fellowship training and sit for the boards.