Struggling with deadlift form due to lowerbody problems

Yesterday was the first time I tried deadlifting. I managed to lift 80 kg, but it put all the strain on my lower back. My lower back was rising before my upper back. I watched Squat University’s video, but I’m struggling to get into the proper deadlift position due to my long limbs, short arms, and a very tight lower body.

I also experience a sciatica-like current-passing sensation below my hamstrings and feel some pain in my adductors when attempting goblet squats. How can I fix these issues? What exercises would help?