A garage without heat is a constant source of condensation in this time of the year. A warm day with a little humidity, then a temperature drop after dark will make a wet spot before morning. In my garage/shop, The condensation seems to have an appetite for my expensive hand tools and stationary machine table tops. Every spring I have to sand, polish and wax everything that rusted. Amazingly, the cheaper the tool, the less maintenance it requires. ? Back on topic though, do you have room to install a ceiling fan? Air movement seems to help. A separate heat source out in the garage would stabilize the temperature, but the cost would be a major factor. DO NOT try to heat your garage with a branch vent from your regular heat source. Exhaust fumes will find their way into the house by back flowing through the system when the unit's fan is off. Brick walls extending from inside to outside are a pain. Heat is transferred quickly by brick. When you get satisfied that the leak is fixed, you definitely need to re-insulate. that wall. That will keep the warm damp air from condensing moisture on the cold brick.
Tom in KY, where one day the air is so dry you shock the cat, and your glasses steam up the next day.