I think you can get your health OR shields close to 1000 or above (depending on whether you take health-boosting armor or shield-boosting armor).
Damage Reduction will, uh... reduce incoming damage, effectively giving you more shields+health.
So you start with 500 health and 500 shields.
Fitness can give you up to +65% health and shields, or an additional 325 health and 325 shields. (NOTE: At rank 6 you can switch out +25% health and shields for +20% damage reduction for 30 seconds after a heavy melee kill. Good, but not always attainable. This would give you 200 health and 200 shields with a possibility of damage reduction.)
From Intel you can get up to +10% health and +15% shields, or +50 health and +75 shields.
From armor, you can get up to +50% health (all +10% N7 armor) or up to +40% shields (+10% from Sentry Interface, +10% from Kassa Fabrication Shoulders, +10% from Kassa Fabrication arms/gauntlets, and +10% from Kassa Fabrication legs)*. You can mix and max to provide a combination of both. Securitel Helmet provides +5% health and +5% shields and a 100% chance of NPCs to mock you silently for looking like a buffoon.
* Kassa Fabrication chest provides 10% shield regeneration.
The following complete sets of armor provide health and/or shield bonuses:
- Blood Dragon Armor (+20% shields)
- Cerberus Ajax Armor (+25% shields. Also provides +10% shield regen speed.). DLC armor.
- Cerberus Assault Armor (+20% health, +10% shields)
- Cerberus Nightmare Armor (+20% shields. Also provides +20% shield regen speed.) Citadel DLC armor.
- Cerberus Shade Armor (+10% shields. Also provides +10% shield regen speed.) Citadel DLC armor
- Cerberus Spirit Armor (+10% shields. Also provides +10% shield regen speed.) Citadel DLC armor.
- Collector Armor (+20% health, +20% shields. Also provides +20% shield regen speed.)
- N7 Defender Armor (+10% health, +10% shields). Pre-order exclusive
- Reckoner Knight Armor (+10% health, +10% shields). Complete the Kingdoms of Amalur demo.
- Terminus Assault Armor (+30% shields)
So after all that, for a tank Shepard, I recommend:
1) +65% health and +65% shields from Fitness
2) +10% health and 15% shields from Intel
3) From armor, I recommend +30% shields from Kassa Fabrication armor, and then +10% shield regen speed from Kassa Fabrication Chest and another +10% shield regen speed from the Capacitor Helmet. For the Geth Dreadnaught (and earlier until you get all armor pieces), the Collector Armor for +20% health, +20% shields, and +20% shield regen speed.
So for customizable armor pieces, this would give you up to +75% health and +110% shields, or a total of 875 health and 1050 shields.
For the Collector Armor, this would give you up to +95% health and +100% shields, or a total of 975 health and 1000 shields.
Tech Armor will give you up to +50% damage reduction. Fortification will give you up to +40% damage reduction. This is a total of +90% damage reduction. There is a -40% damage penalty out of cover, so out of cover you essentially have up to only +50% damage reduction with both Tech Armor and Fortification active.
You can get +15% shield regen speed from Fitness, +15% shield regen speed from Fortification, and up to +20% shield regen speed from armor, for a total of +50% shield regen speed. You can get another +5% from Intel.
I think the passives for Kaidan and Javik have a squad bonus evolution for +15% and +20% shield regen speed, but I have no idea if these actually work for Shepard or not.