If you're taking orders, dealing with clients, doing installs, CNC work, painting, operating all the printing equipment, doing all fabrication..you're not an installer.
I started in the same position, doing just digital printing... Now I bounce around and do everything above where / when needed, and my official position is manager. If they tried to call me an installer and pay me installer wages, I'd be gone!
I'm in Vancouver - so I'm sure it's a higher cost.of living... But it's dependant.
Our signmaker who does wraps and stuff occasionally is in the $27 range. The sign shop down the street has a guy who only does wraps, and he makes about $35 an hour.. and tried to poach our guy for the same, luckily our guy would rather die than wrap 8 hours a day.
Being a "manager" / jack of all trades, you should get more. If the owner is gone for 6 months and you're running the business, you're effectively a manager. Whether you're managing 1 employee or employees.
If he wants to be an absentee owner and put all the responsibility on your shoulders... Demand more money. If he refuses and he's paying you the same wages you can get elsewhere for half the amount of work, apply and walk away.
Check indeed and Craigslist, look for sign installers, or wide format operators - most pay range in our area is $20-30 an hour.