1: You earn favor points by playing games. You obviously get more points based on your performance in that game.

2: No, you can only use 1 favor item per game.

3: You have to be using a General type Demigod and purchase the minion idols to summon them.

4: No, killing regular minions does not earn you gold. 

It may just be a small amount, not sure.

You do get gold from killing portal grunts like minos, priests, catas, angels, and giants.  You do not get gold from killing a General's minions. 

I know in previous builds you also got gold for destroying buildings, but that might have been removed since I don't see it in the manual?

They give no xp

Well the risk would be heavy AoE which would leave your Demigod in a less-than-desireable state. I've been playing Erebus yesterday while the servers were migrating, and he can do a ton of damage with his Nightwalkers (not to mention they heal him at max rank), but if they're nuked it's just him, and a lot of damage output is taken away.

Having replaceable units die quickly doesn't qualify as a risk, imo, because all you lose is the (short) cooldown time and the mana.  You can afford 15 seconds at your crystal.  There are no gold or xp penalties in losing minions.

Outside of initial outlay, mana cost, and cooldown there's no risk in a traditional minion build as long as you can survive long enough to raise another batch.  Now that we have effective minions that's actually a problem - Generals can sit back and summon heavy units all day long at minimum expense. 

The only things keeping minions from being insanely abused right now are their awkward interface and slow tactical responsiveness, imo. 

Two quick fixes would make it all work out -

- Idol minions need to die when their idol is sold (4 sets of priests who all have seperate cooldowns on their heals - OP.  Multiply that by the number of Generals on your team - Priceless)

- As well as mana, every idol minion summoned should have a gold cost equivalent to their level.  A level 4 Bishop should cost 200 gold to summon, every time.  Alternatively, minions killed should render gold and xp.

Well, not necessarily. I mean, it's true for idol minions to an extent, but if you build your Demigod with minion-specific skills (Erebus for example has 2 skills for the minions, and his stat upgrades buff minions). Then, say, you pick equipment and favor item that enhances minions at the expense of personal stats (though at least armors tend to do both).

Now you invested pretty heavily into buffing minions at the expense of personal power, so if your minion army is AoE'd down early in the fight, you lose a significant portion of your DPS, and leaving you much more vulnerable in some cases (QoT can sacrifice a shambler for hp, Erebus' minions heal him, Oak's buff his damage). If you win that fight, sure you can easily replaceme them. But there's a high chance you'll lose that fight as well. And that's the risk: a General with a skill/item build around his minions is weak without them but powerful with. Losing the minion army early in a fight hurts.