Let us go over your points one by one
1. You are making a blanket statement here
" Let's see, KSA (one of the largest weapons purchaser / importer in the world right now), won't buy anything air worthy from Russia or China. "
Saudi Arabia has purchased intermediate range ballistic missiles from China. This was during the 1980s. Why would they not do business ?
China–Saudi Arabia relations - Wikipedia, the free encyclopedia
UAE, Jordan have ordered state of the art SAM systems from Russia
Pantsir-S1 - Wikipedia, the free encyclopedia
Why would China and Russia miss a chance to improve their relations with Saudi Arabia ?
"There are many European countries like Serbia, Lithuania, Greece, etc, who were Russian friendly during the times of the Eastern Europe.....but now with the European Union in place, life's changed for Russia, and has become a LOT more difficult, (if you don't follow the news)."
2. Let us go over the case of smaller European countries.
Lithuania will order American equipment to stay on the good graces of Uncle Sam. Greek air force is completely Western aircraft. Serbia has no air force.
What makes you think some of these smaller European countries cannot build their own cheap aircraft ? Serbia has high quality engineers to build their own aircraft. They have better access to Western technology if they do not involve Pakistan or China. Czech Republic makes the L-39/L-159 jet trainers.
" Next, there are thousands of Mig's and F4/5's and Chinese versions of jets like the F-7, etc, which need replacements. And not all countries can buy the later 3rd Gen or 4th Gen jets, and not many countries offer high end BVR missile and JDAM, ASM, JSOW type capability in the price tag you can get a new JFT for, with said capabilities. So you don't need thousands of JFT's sold and no one's said that. But mere 500-1000 overall sold, long term, is very much doable, and enough to change the Pakistani aviation industry to a much higher and advanced levels. The profits from sold jets will be used for further r&d and in coming up with newer platforms."
the whole idea of selling jf-17 to 3rd countries has been around for 5+ years. i have not seen a single deal done.