Red, that ain't no "training wheels" learning tree. If you recognize that your out of your comfort zone, good on you. You have a good head on your shoulders.
The pros here (and pseudo pros) may claim its a no brainer. Looks to me like a big potential to barber chair. And if its 4 ft diameter 18 ft up, it's a big, big tree.
I can't say this loud enough: BE ALERT ANYWHERE NEAR THAT TREE. If you think it's making noises now, wait.
Final thought: if you wonder why so many farmers are seriously injured or killed, its a failure to recognize or respect danger outside of your expertise. Don't get dead from ignorance.