Pin, clamp, pin, clamp until everything is straight. You should be able with the clamps and pins to get everything straight and square. It may bow upon removal at this stage. But as you complete the wing, adding the webs, the sheeting, the spars etc. if you clamp and glue everything straight at every step the structure will be straight. The sheeting step often "sets" the wing straightness.

I do not consider the bow in the spar you describe as being unusual or a gamebreaker. Make sure you have plent of pins and clamps.