New 220V outlet for expansion?
You should wire in a sub-panel at/near the "guest kitchen" (current terminus of the 4Ga wire.) 

That sub-panel would be where you move the present 30A breaker to, for the outlet feeding the stove (only.) You feed that sub-panel with a breaker suited for the wires feeding it (copper being higher than aluminum for the same size) and the temperature rating of the wire insulation or terminals (whichever is lower rules.) 

The sub-panel should have adequate space for the 30A breaker for the stove,  a 15A breaker (circuit for your 5A motor) and a 50A breaker (circuit for your 50A welder.)