Preheat a grill to medium high. Whisk together the chipotle powder, cumin, orange zest and 1/2 teaspoon salt. Toss with the salmon and set aside.
Meanwhile, cut off the tops and bottoms of the oranges with a sharp knife. Place cut-side down, then cut off the peel and white pith. One at a time, hold each orange over a bowl and cut along the membranes to remove the segments, letting them fall into the bowl. Squeeze the juice from the membranes into the bowl. Chop the orange slices into small pieces, then return to the bowl. Add the avocado, red onion, cilantro, jalapeño, lime juice and a pinch of salt; toss well.
Lightly oil the grill and add the corn. Grill, turning occasionally, until charred all over, 12 to 15 minutes. After a few minutes, add the salmon to the grill and cook until well marked and charred at the edges, about 2 to 4 minutes per side, depending on the thickness. Grill the tortillas until marked and warmed, 20 to 30 seconds per side.
Cut the corn kernels off the cob and toss with the avocado-orange salsa. Divide the tortillas among plates and top with the salmon, salsa and more cilantro. Serve with the lime wedges.