Plug appears loose, gasket not seated as CAN see it. Should be to the flywheel area so not so much issue.
Agreed. However worth putting right while you are in there. Also a good clean with some degreaser to remove all the oil residue.
Maybe now is the time to set the oil level correct (simply somewhere between the ADD and FULL marks) on the Engine Idling side of the stick with the engine actually running and oil at normal operating temperature.
Run the engine with the belly guards off (maybe even some light work on good ground) and see where the oil you saw before is actually coming from...?
Based on what the OP has spoken regarding the way his brother was checking the oil level in the past I would be hopeful that the engine was simply overfilled and so has been puking the extra out from various orifices.
Good points made by other BTW regarding most engines having a "sweet spot" on the dip stick. Fill the oil above that and the engine will just puke out the extra until the oil level gets back to where it wants to be.