Having been through the area quite a few times, you might consider taking I35W through DFW and jumping over to I45 using US287. As for Houston, the only way to avoid it is to take Beltway 8 around, which is more miles and requires tolls, but much less aggravating. If you are going around to I45 to Galveston, the tolls on the SH8 bridge over the ship channel are quite expensive. Going I610 around doesn't seem to avoid much traffic, though it is not as many more miles since it is a tight loop. It does save on the tolls however.