Should I be worried about getting canned?
I presume you are asking if the chances of you getting fired are higher because you are being paid more than your colleague. Not necessarily.
Companies have a payscale for every role / designation, and if you are being paid on the higher end of the payscale, it is because the company values your skill more. Note that companies don't just value someone purely on their technical skills and qualifications. It could also be your work ethics or your loyalty or your social skill or your ability to please / upsell more to your client etc.
The real issues are:
- You not having a good professional rapport with your new manager.
- Your insecurity that you aren't fully competent at your job.
This is what is causing you anxiety and worry, and that's where your full focus should be.
Dealing with your Managerº:
Note that it takes time to establish a good working relationship with anyone new. Just because your new manager micro-manages your work or is critical of some of it, doesn't mean that he dislikes you or is out to get you. That may simply be his style of managing people, unpleasant as it may be to those under him. (Perhaps he himself is new at this and is dealing with his own insecurities of learning to manage people).
Rather than doubting or speculating about this, go have a frank chat with him. Request a meeting and talk directly. For example, you could tell him - "I noticed that when you assign any task to me, you pay a lot of attention to it, even overseeing it. Is this because you feel that I am not yet fully competent at that particular task and have a lot more to learn?".
A good manager will politely clarify your concerns, and even try to address it to a certain extent.
You can (and should) even ask for his help - "I realise that I have to upskill in so and so area - I'd certainly appreciate it if you tell me what your expectations are from me in so and so area and what I should prioritise learning to make your job easier? Could you suggest some good resource, like a book or online resource, or even someone else that can train me on this subject?".
Your job is to make your boss' job easier. So it is important to understand what his specific expectations are from you. (Good manager are upfront in communicating this to you. With others, you have to use your own intuition and experience to figure out what pleases him). It is also helpful to realise that people who micromanage others tend to have anxiety issues. That is why they don't fully trust people to do their assigned tasks and involve themselves too much. You just have to slowly build trust by meeting his expectations.
How he addresses your concern will tell you a lot about him. Worst case, he may just be a jerk, in which case you will be stuck in a lousy work environment.
(Note that such a meeting may not necessarily be a one way street - your manager may quiz you too on what your future goals are and what you like or dislike about his style of management. Be prepared. Be diplomatic, but don't sound like you lack confident.)
º I am going to assume the manager is a guy.