Two Ythretvarian pennies worth:
Magnum, it's true... you can get very varied results from similar settings because of the complicated interactions that take place with other factors you only have indirect control over. Some of the bad advice you've gotten in the past may very well have worked under different circumstances. Remember, as president, you will likely have a better idea about your economy than someone answering a particular question. Your main job as president is to figure out which technique works best for your country at the present moment. That being said:
I'd recommend not purposefully lowering your ed index. This index not only helps your score when you're plying for ranking, but it also tells CEOs your country can continue to staff their corps in the future. Most players dont realize, and most of the other players forget from time to time including myself: your population is constantly changing. Workers retire, become disabled, and some just die and must be replaced with newly graduated workers. If you drastically lower your ed, you may have enough workers today, but as they retire your ed wont be able to graduate enough new workers to fill the openings. Then you all of sudden notice large numbers of corps suffering worker shortages.
As your economy grows, I'd recommend purposely keeping a nice large pool of unemployed workers in each class, just to help replace retirees.
Populations over 50 million also require a higher health index than smaller pops. Apparently, it requires much more healthcare per citizen to keep a large country healthy than a smaller country does. (Suppose it makes some sense since realworld illness is so closely linked to population density.) Large countries with low health suffer pop loss until a new balance is found. Of course, this can be the cause of lots of headaches. From my understanding, pops over 50 million require a health index of 150 or greater to remain stable. Moral: strengthen your mind and body.
I'm not sure your military indexes mean much beyond your score since you cant know for certain what your opponent's strengths are until you goto war and encounter them. You simply have to prepare for war if youre going to war. I don't think there's really a "good number" you should "keep" them at. Different presidents at WL3 have drastically different defense capabilities. (Not to mention you have no idea what they have offworld that they can fly in to reinforce themselves.) The only "for sure" defense advice I've come across is: have lots and lots of nuclear defense. Seems like nukes are the current weapons of choice in many PvPs.