Unikernel is kind of the opposite of microkernel, though; a unikernel merges the application "upwards" into the kernel, while a microkernel system tries to split responsibility into lots of not-especially-trusted pieces.
At the same time, a unikernel will usually rely on a unified upstream virtual machine, which a hypervisor will provide, because you're rarely going to run unikernel applications on exclusive bare metal.
In that context you can think of the hypervisor as your microkernel which provides a unified but very low level API to the unikernel-based microservices.
Yes. Whereas in a traditional setup you'd have an "OS" running an "executable", the hypervisor-unikernel setup the unikernel plays the role of the executable. This indicates that something is very wrong with the OS APIs that this is considered the best way to arrange the desired isolation level!
In that context you can think of the hypervisor as your microkernel which provides a unified but very low level API to the unikernel-based microservices.