Upload & Sell: On
"I had a guy offer a custom profile to allow me to work at a higher luminance and have my prints match better. All he did was lighten the image from a test pattern I printed for him. It works pretty good but not for all images."
Well, lightening the test target would make your prints from the resulting test target darker, not lighter, plus it screws with the patch values which makes the profile correction wrong as well. I've been making custom profiles for something like fourteen years now and have rarely had to make tweaks, and never to luminance, once in a while to compensate for the yellow/green bug I discovered in ProfileMaker, and a couple of times to adjust the white point of the Absolute Colorimetric table for more accurate soft proofing of offset press proofs.
"I have no control over the light I use to display my images. It is a mix of sunlight and interior light. I can change my display calibration however."
"I use 6500 not 5000 I am surprised you mention 5000. "
5000K is the viewing standard. There has always been a discrepancy regarding what it takes for the white point of an emissive display to visually match a reflective print. Most people find that 6500K on the monitor more closely matches 5000K in viewing, so they go with it.
"I originally went with Red River because they sold 17x25 cut sheet paper and nobody else did. I have not checked lately. I suppose I could see if Epson has 17x25 matte."
It seems that Epson only sells 17x22, but for purposes of testing and sorting out your color/luminance issues, that would be fine.