Your end caps look the same as what we had on the 2005 26Q. We have since sold the 26Q, so I am working from memory
and what pictures I have.
I do remember that we had a split in the rear end cap, just like yours. I eventually put a small strip of Eternabond over it in an attempt to seal it off. The split was right at the middle clearance marker light. I don't believe that there ever was water intrusion there, though I don't recall ever removing the rear emergency window to verify.
As far as the split on the front cap, I don't recall finding anything like that on our unit. I wonder if they manufacture these caps in two pieces and join them later on. As you said, they appear like a perfect seam, and not a running crack.
As far as repair, I would be looking initially to try and get to the backside of the cap. Problem here is being minimally disruptive to the interior. If you can get back there, I would be thinking of fiberglass (and stiffening with wood or other material). Alternately, you could try 3M 5200 adhesive with some backing material. Clamping a 5200 repair might take some ingenuity. Really need to understand what the cap material is, to figure out what kind of repair may be possible. If the exterior look of it bothers you, maybe it is time for a racing stripe.
My preference would be to not remove the whole cap and replace with a new or repaired part if I could avoid it. I would hate to introduce any new issues putting it back together. I did a full cab over repair on an 84 Mallard Class C we owned prior to the 2005 26Q, and it was a lot of work. Alignment of the sides and front panels may change when you remove the cap. If you do remove it, and want a professional repair, you could take it to someone who repairs gelcoat fiberglass boats. Possibly, they could do it without removal. Just a thought.
Have you tried contacting REV about parts? Probably not available, but maybe they can give you a lead.
Your other option is to try the RV salvage yards, such as Colaws.