Hi have you had a MRI of the area? A CINE MRI to check CSF flow?
If not, ask your Dr about checking with these tests as it could be a restriction of flow causing the heartbeat issue..and a flow issue since the symptoms are exacerbated when you tilt your head.....
You may want to see a neurologist or a spine Dr to see what they may find.
Im 52 years old and i have had ringing in both ears and have good hearing.I have the ringing for about 7-8 years. I went to see a ENT Dr and they checked for vertigo , but wasn't. They told me I needed some kind of cranium therapy. I get light headed and sometimes dizzy like I'm going to lose my balance. My head/ears feels like its full of air, or maybe they're my ears.I have tried to ignore that i have the ringing in my ears.When its quiet is when i feel it more. Now i feel scalp pain and head tension pain, a head ache.I feel it on the crown of my head . Don't know what it could be. I have been tinting my hair every month, and used a stronger developer. My head feels like full of air or it could be my ears. I made an appt. with my doc. Will see what he says. Anyone felt like that before, ' PLEASE any comments!!