How to increase veroboard's current capacity?
You could either run jumper wire on top of the veroboard, or another good way would be to solder on solder braid (its made of copper) to "append" more copper onto the trace. 

Something like this:



The current carrying capacity is determined by the cross sectional area of the conductor so if you can estimate the cross sectional area, you could determine the amount of current it could carry.