i believe the research and economic % are based on your basic income, your total income is base income + every bonus like economic buildings, super projects, race abilities, mining resources.

so if you have 100 dollars and 100% economic % you get 200
if you than take a economic mine and get it to 9%, you get 100 dollars + 109% = 209 dollars and not 218.

with moral, the 15% of the building i believe is correct but if you have your tax at a certain point and a high ammount of pop your moral will go down.
so lets say you have 80% tax and 30B pop 1 moral building will only increase moral by 1%.
the 15% is only at low pop and very low tax wich you will never have.

Mystic is basically correct but a little off on the morale. Also as Tertullian referenced, the Wiki will give you a lot of this.

The morale benefit of any building is multiplied by the "base" morale of the planet which is determined by the population. Basically from the wiki morale article:

Wiki GC2 Morale

Population in billion // fBaseMorale (In-game "-??% From Population" in Approval's Tool Tip)

1 b. // 99 (-1%)
5 b. // 91 (-9%)
10 b. // 77 (-23%)
15 b. // 60 (-40%)
20 b. // 40 (-60%)
25+ b. // 20 (-80%)

So for example a morale building that gives a 15% bonus, actually gives the following bonus at each pop level.

1 b. // 99% * 15% = 14.8%
5 b. // 91% * 15% = 13.6%
10 b. // 77% * 15% = 11.6%
15 b. // 60% * 15% = 9%
20 b. // 40% * 15% = 6%
25+ b. // 20% * 15% = 3%

Say I've got a 700% bonus farming square. My planet population can get up to aprox 30 billion. How do I keep them happy?

Depends on the level of your taxes and it gets pretty complicated. But at zero taxes with no global civ morale bonus from ability, techs and morale resource mining, your morale would be 20% + 20% * (planet morale bonus). If you wanted a 100% approval and assuming the Virtual Reality Center gives a 40% moral bonus you would need 10 VRC's (20% + 20% * 10 * 40% = 100%). With some level of global morale ability this would be reduced, but the global morale ability is also multiplied by base morale (then taken to the .75 power as well). The short answer is it's probablly not worthwhile to try to get your pop so high and I would *never* put a farm on anything larger than a 100% bonus tile.

This is funny. I had trouble with the post not going through all in one piece, it kept hanging on me, so I broke it up. Apparently the aborted posts did get through anyway. Sure wish I could delete some of these posts. Sorry.

Don't really know how the broken up post got sandwiched between the others because those were definitely the last post's I made in the thread.

Say I've got a 700% bonus farming square.

There are no 700% bonus farm tiles, only 100% and 300%.