He loses all abilities. Indestructible is an ability, so he is no longer indestructible.
As for the difference between keywords and ability words, it's actually pretty simple:
- Keywords have rules text embedded in them, like flight or trample. All you need is the keyword.
- Ability words do not have rules text embedded in them. They are as important as flavor text, from a game perspective. Ability words just tie mechanics together, like metalcraft or ferocious. Ability words don't all have the same rules meaning, they just group related abilities together. As such, they always need actual rules text following them explaining the ability. Just check out a couple different metalcraft cards. They all relate to 3-or-more-artifacts, but the effects of them are different. 'Metalcraft' doesn't mean anything to the game, it's just there to let the player know thematically that it's similar to other metalcraft abilities.