D.D.
Yes, this sounds like GERD, especially the arching and crying.
One thing to consider - GERD is very often greatly exacerbated by food allergies. My GERD baby was completely intolerant to cow's milk. And yes, I breastfed, so this meant absolutely nothing with milk it in for me - no milk, cheese, yogurt, or anything with casein as an ingredient. I strongly encourage you to try a cow's milk elimination diet for 2 weeks. Even if it is GERD, you may be able to lessen the symptoms by changing your diet.
Another classic symptom of GERD that I think you've posted about - breastmilk is a natural antacid, so GERD babies like to nurse frequently. Especially when you lay them down - laying down at night=more heartburn for them because fluids come up more easily=baby wants to nurse every hour at night because it soothes the heartburn pain.
Other tips for a potential GERD baby (free to try, so why not): hold the baby upright for at least 30 minutes after feeding, feed less food more often, and prop the crib so it's at an angle so the baby isn't laying flat. My guy also did a lot of napping on me in the Moby wrap.
Some tips from the breastfeeding mom's bible, kellymom.com: http://kellymom.com/health/baby-health/reflux/
OH - unrelated to tummy time. Refux babies often feel better on their tummies than on their backs. In my experience, some babies just hate tummy time, regardless :)