Actually he is doing you a favor by not using the install from the webhosting company. The way to make sure that he does not control you server and domain is to grant him a separate user access that is not connected to the billing and main user sign on, but some web hosts do not offer this feature tho cpanel has made some strides in this area. If they offer this and how to use it, is what to ask of both your domain and hosting providers.
The other thing to ask is if you do not trust him, why did you hire him?
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