Need advice about the expanding role I'm being asked to fill.

Since I have started as the network admin at my local municipality, we have made some nice strides in terms of security. I designed and rolled out our VMWARE nsx firewall to protect East West traffic. I am currently in the process of separation of public traffic off our internal network by means of a new circuit and firewall. We also hired a new managed security vendor that has brought to light a lot of blind spots in our security.

I am seeing a more expanded role in security and while I love the challenge and learning opportunity, I feel like I'm getting overwhelmed and compensation for all this work seems hard to come by.

I'm not sure how to ask my management to either promote me to full time info sec engineer or hire someone from the outside to do this because I'm finding I have no time to be an administrator since I'm working all the time on projects and security related things.

I don't know of how to pose this to management in an eloquent way where I'll be taken seriously. Any admins out there can share their experience with being in charge of security? We currently have 2 edge firewalls(1 more on the way to be for public traffic) 1 internal fw protecting public safety and the next firewall for East West server traffic. Also...my sys admin keeps trying to dump the endpoint security on me. Any advice would be greatly appreciated. I can take any criticism as well ;)