Q: Can I give a hero more than 5 hero abilities with triggers?
A: Yes and no. If you give the hero the ability they'll receive the ability at level 1, and they won't be able to put points into it. In order to make the skill a higher level, you'll need to use the upgrade editor to make an upgrade that's an ability bonus, and specify the ability as the ability it applies to. Also be sure to add the upgrade to the Upgrades Used field of the unit that will use the ability. Then, to increase the ability's level, use triggers to increase the research level of that upgrade.