Do you have any people working in IT besides you? If not its probably a bad idea to shift everything to inhouse. Management gonna like it up until something happens. And their is always something that will happen in the fast moving IT world. Do you have multiple backups inplace? Any offsite and immutable? Any person besides you who gonna regularly validate them and fix them if problems arrise? If the answer to any of this is no, don’t do it. Their is a reason for these it solutions s provider and why their are usually not cheap. Just find someone better instead of trying to cheap out.

If proxmox is too difficult I would probably remove pretty much every open source options and move to something like synology since it seems like youre working at a small company.

Proxmox offers paid support though and is a finished solution. Since the vmware acquisition multiple people I talk with moved some of their systems to proxmox.