I know I'm a bit late to the discussion, but I recently played a game as the Jotnar and thought they were quite playable, just very different from the other civs in the game, so thought I'd offer my impressions.
Surviving an early game rush is definitely doable. Egrass is quite a strong unit, considering how early in the game he comes. Jotnar Citizens can defend themselves. And Thrall Militia are cheap defenders that you can crank out quickly: when fortified in a city, they have a good chance at defeating an attacking barbarian unit. Any surviving attackers will be weakened and vulnerable to a counterattack from Egrass. And you can always move your science slider to zero for a few turns to accumulate gold to upgrade a Citizen to a combat unit.
City placement: because of the 1-ring limitation, no single city is going to be an economic powerhouse, so you compensate by building several cities close together -- ideally, two tiles apart, to use every square. Won't always be able to do it, depending on geography, but that's what to shoot for. So in the aggregate you should end up with a decent economy.
City management: The 8-population limit means that you should manage your cities to produce exactly 16 food. You get +1 food from farms, windmills, and watermills. Agrarianism gives your farms another +1 food, as does researching Sanitation. Most of your cities, therefore, will probably not need more than 2(!) farms, depending on terrain and bonus resources. The other 6 tiles can be filled with mines and workshops for production, cottages for commerce, or windmills and watermills for a balance of production and commerce. So you should be able to get decent production.
You're not likely to build many wonders, if any (unless you pop a Great Engineer from a lair or an event), so instead you adopt a strategy not focused on wonders. It might be worth trying to build some, anyway, since if you fail you end up with gold that you can use to upgrade your units.
As for religion, the 'pedia recommends RoK for the gold. Another possibility would be OO, since it allows upgrading your surviving Thrall Militia to the somewhat more useful Drown. (In my game I went Empyrean, since nobody else had and I thought it would be fun to get Chalid.)