Form I-140 Premium processing can be done along with I-485 concurrent filing. that way you can get I-140 decision within 15 days. Current I-485 processing time for Texas Service Center is 8 month and for Nebraska center is probably 3/4 month. Don't worry about those stuff before perm approval coz that's the frustrating part of the whole process. You can travel out of State once you have approved AP, which you'll get way before getting GC. All the Best.