Job Interview for similar position similar pay should I offer what pay I am seeking?

Current Job situation:

I really enjoy my job for the most part, I am part of an IT team of 2 including me and my IT Manager for 50 newspapers across KY-IN-TN. We manage users and locations and we are managing our main hub with servers and cloud servers. There isn't much opportunities for IT in my city so I figured I would apply and see where it goes. Currently I make $17/hr full-time with 2 weeks paid vacation, Health/dental is too expensive for me to be a benefit. So benefits will be a factor between both jobs. I feel like I should be getting paid more than I am and I have been working for them for 2.5 years and I had 2 raises. 1.) I had to quit and then they offered me $1 more an hour if I came back which I had accepted cause the job I had been working at had horrible management. 2.)Then one year later I got another $1.50 raise due to consideration and year-end budgeting. They are not known to give out raises and there is potential to get more, but my IT Manager said to not expect it. We have a lot more work than we used to. When I started we had 20 newspapers to manage we added 30 more and they keep coming too. I am also seeing retail workers in my area making $18/hr full time which irritates me. I definitely think they may try to counter offer me which I would consider because they have been losing a lot of staff at multiple locations due to better job opportunities. I know losing me would leave the IT Manager by himself to manage all locations. There is a lot of things and projects going on and I do feel bad but in the end I need to think about what is best for my career and income.

​

Job Considering:

I have an interview for this position coming up. I am overqualified for the position, it is an IT Assistant for a Catholic school district. Pay is $18/hr. I have heard benefits are good but what is alarming is they are hiring for an IT Director and two IT Assistants. Just don't see why they would need a whole new staff. I am wanting $20/hr or more is this reasonable to ask in an interview when pay comes up? The listed qualification on the application is an Associates Degree in Information Technology. I have that plus one security cert and 2.5 years of experience so I feel asking $20/hr is reasonable if they don't offer me that considering my experience. Any guidance or advice is appreciated.