I'm glad to hear everything went well and you're feeling better! Unfortunately, it all really varies. You need to give yourself a good 4-6 weeks for incisions and everything to heal, but the insides and CSF levels can take much longer. I had catheter and valve replaced for my LP shunt last year..they told me to give my stomach 6 months to heal and at least that long for my body to adjust to new levels. Of course they removed old stuff and put in new, so that's probably longer than you'll need.
1-I think it's normal to feel tension and tenderness in your abdomen..they do a lot of work placing the long catheter in there, so your body will need time to heal. Sometimes it feels like stitches are pulling because of the way they heal. Make sure your surgeon is aware, but it usually passes.
2-You probably have swelling and possibly some remaining gas from when they pumped your stomach up for surgery, especially if you haven't been moving around much. It should ease up the more you start to move around. Again, let your surgeon know if it becomes bothersome.
3-The low pressure headaches really depend on how much spinal fluid was lost during surgery and how quickly your body tends to recuperate. Try drinking fluids with a lot of caffeine and lay flat when you're resting..I would think you would start noticing a difference soon. If not, call the surgeons office to see if they have any recommendations or concerns.
I'm sorry I couldn't be more specific, but hopefully some of this at least put your mind at ease...you just need some good old fashioned rest and relaxation!
Wishing you a speedy recovery!!!
Julie