Your battery, back in September, shows 360 battery cycles. One site suggests a battery will normally last for 300-500 cycles. So you are in that zone with your battery.
There is another thread where a battery is draining while in hibernation about the amount a Modern Standby system will drain while in Modern Standby. It is not supposed to drain in hibernation either, but it is.. and the battery only had 56 cycles.
You may have a battery which is failing and along with unexpected drains, will show an accelerated drain. The high number of cycles on the battery may exclude you from being considered for a warranty replacement.
I would still suggest you put your system back to the factory configuration and let it work as designed. It may still drain, but might not drain as much.
I am currently looking at the Surface Pro 6. Before I purchase, I want to know how much it will cost to replace a battery in an $1800 unit. I think the answer to the question may keep me from going down that road.