sciatic issues and biking

I don't have any advice on bike position but personally I'd concentrate on dealing with the sciatic issue first and put training on the back burner for now. It's tough to correct sciatica problems while constantly aggravating it with training. 

^^^ Absolutely correct. I have sciatica on my lower back... I went through weeks of physical therapy while using a traction device. I got lucky and good 'ol Uncle Same bought me my own home based traction device to help alleviate the pain on my lower back that radiated down to my leg. Because I took a break from cycling and all the physical therapy and traction therapy, I am now able to go on long rides in full aero 90+% of the ride without suffering excruciating pain.

As mentioned, I would suggest you take care of yourself FIRST and if you are able to, seek a sports doctor/physical therapist and try the traction unit. Also, look up the stretches online if you do not have a list of them already... Most importantly (if you are not already), take some Vitamins!! Folic Acid, Vitamin B6, B12, Magnesium, especially stock up on Glucosamine and Vitaminc C, D and it will help.

Good luck to you.