The shirt idea?
You probably don't want to be wearing the same shirt every day.
IWB is probably going to be quite uncomfortable for you if you do most of what you said above every day.
If people that you work with do not have a problem with you carrying then you might want to carry OWB - behind the hip.
Then just leave it open or cover it with an oversize untucked Cotton T-Shirt. Very comfortable.
You might want to think about buying a nice firm holster from somebody like M. Sparks with a Steel reinforced insert stitched in the holster mouth.
That way you can have your firearm be tightly and consistently retained without bothering with a retention strap. Your firearm will never fall out.
Your holster WILL get scuffed and scratched but, who cares.
Nothing stays new forever.
If nobody around you cares if you carry a firearm or not then why carry deeper than necessary?