I do not think that the crack in the base gasket surface is a problem.  The coolant leaking into the engine is a big problem. 

Is the crud in the water jackets corrosion or from using a dirty bucket to fill the radiator.

The damage to the head looks like old damage, not something that has happened 5 minutes before it was last shut down. 

Two base gaskets will raise the ports and lower the compression unless a motor builder machined 0.5 mm off the head or base gasket surface and had to use an extra gasket to get the ports and piston to head clearance where he wanted it. 

There are  guys on a lot of forums that recommend adding another base gasket in an attempt to avoid spending money on porting.  Adding a gasket or doing the correct modification to the ports will produce entirely different results.