Hi Welshweyr.
One thing about Kodp to remember, especially about happiness is that there isn't any one solution. If your doing well in one thing, say producing food or winning battles, it will have a knock on effect to how happy your people are, unfortunately the converse is true.
To understand some of the systems in the game the Kodp wiki is rather helpful, however a lot of what you need to know is already in the game. For example, your clan ring know far more about farming, and about the current state of your land than you do, so go onto the farming screen and read the advice, especially of worshippers of ernalda or uralda, they will let you know what needs doing regarding alocating more land etc.
I will say goods production is a good route to success (no pun intended), building up a good markit, getting trade partners and using iseries blessings to improve your traide sinse that way if you have a bad harvest you always have something to sell, indeed if you take care of producing as many goods and cows as possible, the food situation will take care of itself.
Regarding mysteries, firstly, 35 cows is waaaay too much, 10-20 cows or a similarly quantity of goods is a much better bet. Plus, consider whether the god your sacrificing to would prefer cows or goods (for example Iseries obviously likes goods). I wonder are you sacrificing correctly? You need to make sure that the radial for the God and! the radial for the mysteries is checked when you sacrifice. Also, note that it's far more likely to work if your sacrificing to a god who you either have a worshipper of on the ring or a shrine to, or both.
As regards quests, if your going by trial and error your not doing them correctly. You first need to carry on sacrificing mysteries to a particular god until you have all the knolidge of the myth (when it says "so and so has revealed the secrets of the such and such myth"), then you should read the myth and be familiar with it, sinse that will give you the best idea of likely courses of action. If your very stuck the wiki has pages for each quest listing the choices and chances of success, though note "chances" is the operative word here.
Dedicating magic to quests, (and remember if you have a trickster on the ring you can dedicate two points of magic), and having a quantity of clan magic in reserve also have an effect. Plus, note that you can't attempt quests too often, if your failing to get your quester into the realm of the gods that might be the reason why.
The making of the storm tribe and ernalda feeds the tribe quests are imho the easiest, indeed making of the storm tribe is the quest you need to do in order to start forming a tribe with other clans and progress in the game.
Hth.
Kodp is not an easy game, particularly sinse you sort of need to start thinking in an Orlanthi fashion to get the best outcome of various events, (listen to your ring's advice). but it is well worth the trouble, indeed I don't think I've had a game absorb my attention so completely for quite as long as I have when playing Kodp last summer literally for about 18 hours a day for four days! Indeed, that is why I am having something of a break from Kodp at the moment.
With our dreaming and singing, Ceaseless and sorrowless we! The glory about us clinging Of the glorious futures we see,
Our souls with high music ringing; O men! It must ever be
That we dwell in our dreaming and singing, A little apart from ye. (Arthur O'Shaughnessy 1873.)