Well good luck, but I have some advice for you. You had difficulty with an aptitude test and although a certain level of basic knowledge is required in order to complete it, it really is not a test of knowledge. It's a test of your ability to understand certain types of things and work things out. It's good that you were able to study some stuff and go into it better prepared, but the fact remains that you struggled with it. You have chosen a number of very technical trades and I would predict that you will struggle with the training you may be about to undergo. Think about the test you just completed that you had months to prepare for and which you had already done (different questions perhaps, but much the same type of stuff). Now think about learning completely new concepts and the test is at the end of the week. Be prepared!
The fact that stewards can be enrolled with "lesser" aptitude scores does not mean they are less bright than others. It may simply mean that their brains work differently than other people who are more technically inclined. Just because Winston Churchill didn't develop the theory of relativity doesn't mean that he wasn't as bright at Einstein any more that calling Einstein a moron because he didn't write a history of the world.
Steward is an honourable trade that has been reviewed on several occasions to assess its viability and necessity. It's still here and the people who do it are full and active members of the Canadian Armed Forces. Some are on active operations at this very moment and they are just as much a contribution to mission success as anybody else. It may not be a trade you're interested in, but you're not "better than that."
Good luck to you for the future.
From a guy who supervises stewards