1. Sort of, yes. As a tank, you have your main 1 2 3 combo, but then there's other combo skills you can use. If you use those, you can break the combo. I also believe Shield Bash breaks the combo but I'm not 100% on that because I never actually paid close attention to it. Now, buffs and off GCD skills, such as Rampart, or Circle of Scorn/Spirits Within, and I believe Flash do not break combo.
Of course, you can always try it out on the dummies right outside Ul Dah in West Thanalan.
2. While you're leveling your tank, try to just invest in gear that is only equippable by GLA/PLD MRD/WAR. This is assuming you feel like you need more VIT and Defense. It'll be labeled as such, and there is new tank gear sets available to you every fifth level. I personally upgraded every fifth level while leveling my tanks because I was able to craft my gear which made it very cheap. To get these sets, you can either purchase them off the marketboard, or ask for an Armorer to craft it for you and bring them the materials and then tip them. The latter is usually much cheaper and it makes getting HQ gear much easier.
