You've been attempting to get a handle on First, Third and Ominscent POV, and now there's yet one more to worry about, Deep POV. I can relate to your frustration. But as I've said in the past, though difficult to master, Deep POV -- the technique of going deeper into your point of view character -- is guaranteed to enrich your writing.
Here's examples of each POV:
FIRST: When John returned, he found me sitting on the white leather bench. I had my eyes half-closed, my arms crossed, and I was feeling great sadness. "Well?" I asked, but I was thinking, 'Give me a reason not to kill you.'
THIRD: Matthew sat down on the white leather bench and lowered his eyes. Consumed by a great sadness, he crossed his arms and waited. When John returned, he asked him, "How long have you worked for me?"
OMNISCIENT: When John returned from summing a plane to pick up his boss and return him safely to the mainland, he found Matthew sitting on the white leather bench with his eyes half-closed and his arms crossed. Matthew chose not to look at him, he was that angry. "John, tell me I didn't make a mistake bringing you," he said. John couldn't think and stuttered...
DEEP POV: The bench in the stern of the boat reeked of that new leather smell that burned all the way down his throat. A glimpse east and the sun's glare shot pain through his temple. Closing his eyes helped, but the trembling wouldn't stop. His pulse pounded through his crossed arms. This was John's fault. No respect. No gratitude. Hadn't he and his daughter been taken care of all these years. Ruby held a secure job at the Baja Hotel for the rest of her life if she wanted. John threatened that. Could his stupidity be forgiven without costing the organization everything? A touch of the gun and the chill felt shocking at first, then comforting.
DEEP POV is a combination of first (intimate) and third (limited). As silly as it sounds, the only way to succeed in pulling your reader into the experience of your POV character is to become THAT character. Close your eyes, experience the totality of that character, then open your eyes and start writing.
If that's too difficult, start off by writing a scene from FIRST POV, then switch it to THIRD POV. Drop as many verbs as possible, (saw, thought, looked, etc) eliminate the tags: said, asked (no need to show the reader what they already know). Do this for every scene, and I promise it'll start becoming as natural as riding a bike.
After a few exercises, let me know how you're doing.