What it is the maximum "real" current by the collector that can be drawn from ULN2067B
Besides maximum current through one darlington transistor you also have to care about power dissipation. The datasheet tells you that the saturation voltage of one darlington is up to 1.5V at a collector current of 1.5A, leading to a power dissipation of 2.25W which is alread more than is allowed at 70°C Tamb. If you manage to cool all your pins down to 90°C a total power dissipation of 4.3W is allowed according the absolute maximum ratings. But this is already less that two times 1.5A over a single darlington. So in short: if you load only one transistor its collector current must stay below 1.5A while staying below the limiting power, if you load more, the total power dissipation must stay below both limiting values as well, no matter how you distribute the currents.