Firstly all the issues to your problem can be found in tutorials and everyone I'm pretty sure everybody has expirienced MAX_PATCHES error even the pro's.
I'm guessing you have been reading around and seen that scaling textures is one way to stop max patches. I couldn't find anything in the tutorials on texture work.
1. Select the texture you want to upscale
2. Press "s"
3. A surface properties window should have appeared if not scroll down its beneath the main window where you draws your brushes.
4. Look for the column that says "SX" and "SY" it's in the top right corner of the surface properties window. At the moment both boxes should have 1.0 in them this means they are there original size, change the value to scale your texture.
Example: Putting both SX and SY values to 2.0 means the texture is twice as large. Putting it to 0.5 means its twice as small, Experiment see what works.
With the sky issue you could also select your sky brush(s) and make sure "Sky" is ticked in the surface properties window, other than that I don't know how to help you, unless you didn't do a final compile, if you didn't do a final compile is it because you kept getting the max_pathes error?
Before you realise your map do a final compile.
Here are some words of wisdom from jitspoe (not aimed at you in particular) ;
"Don't release your first map. No offense, but first maps usually suck unless you have some kind of previous experience with 3D editing. I know it takes a lot of time at first, but once you get it down, you can make a new map, beter than the first, in less than half the time. Show it to some friends. Get some feedback, then chaulk it off as a learning experience."