Unsure about root system on Dendrobium Orchid plus a few questions!

[Momo]

Hello, everyone! I just recently took the plunge with my grandmother and bought an Dendrobium orchid! I'm completely new at this so I have a few questions I would love to have answered, if possible.

I brought this little baby home about two days ago. I just love it so I definitely want to do all I can to try and help it thrive. I took it out of the pot since the media was mostly sphagnum moss with a little bark and it was packed too tightly. I repotted it into a bark, perlite, and charcoal mix but I did not water it since it had been stuck up against the wet sphagnum.

First question, the roots. No surprise there, right? Now, I know that brown roots more than likely means root rot. Well, for these guys, they are brown, definitely not white or green like they are supposed to be but they are not mushy or hollow though so are they still alive or are they dead or nearly dead? What should I do with them as far as removal if needed and watering?

Secondly, fertilizing. Should I start using it as soon as I start watering? Or should I wait till I have healthier roots? I have Better Gro Orchid Plus fertilizer at 20-14-13 and it says to use 1 teaspoon per gallon so should I cut that amount in half and use half a teaspoon since the rule of thumb is weakly, weekly?

Lastly, lighting. I have the dendrobium sitting on a table next to a southern facing window. I get sunlight pretty much all day till the sun goes down. Is that going to be a problem for the orchid? I know to watch for sunburns on the leaves but I just wanted to know what people thought.

Thanks in advance for all the help you can give me! I appreciate it!