Man, where to start. Lots of things to tweak here to get you on track, but your goal is very achievable without a lot of macro magic and certainly without drugs.
Do you have a pic?
So do I, no excuses. I'm a total natural bodybuilder with a slow metabolism, still possible to achieve stage-level condition without drugs, to stay lean year-round without drugs, as long as you know how to eat. 10% should be no problem if you have discipline and want to reach your goal bad enough.
Also, just judging by your posts, I think you think you put on fat easily because you're not strict with a consistent nutrition plan and don't have the knowledge of how to structure one. Not trying to knock you bro, just the impression I get. It's quite easy to stay lean, regardless of your metabolic rate, when you know how to eat.
Getting to a true 10% is a lot harder and leaner than most people think. But, again, it can absolutely be done.
This most definitely needs to be adjusted. Keeping fats at 20g is a recipe for screwed up hormones, blood sugar, and tanking testosterone. Protein should be 1.5g MAX. On my most recent contest prep (just finished) I was between 1550-1750 cals per day, so I can certainly relate to your numbers. Keeping protein at 1.5 is the very high end of where you'd want it to be, which is important for satiety, and metabolism. Fats should be at a minimum about 25% of your daily calories. I'd shoot for between 40-50g a day. Lower protein to around 250-260 and make to get your healthy dietary fats!
Where are you getting this number from? That's really very low for a 178lb individual. Are you planning on carb cycling or a steady 80g a day? 80g would be good for a "low day" but performance, metabolism, etc., will maintain better with more carbs.
Yeah man on a well executed cut you should be able to lose 6 pounds in 4 weeks easily, much less 3 months.
I also notice you don't have any cardio in there, might be useful to help implement some.
IMO you should not not not be doing any drugs other than your prescribed TRT. That's a serious decision, and all you're trying to do is cut some weight, not even a lot of weight. If you've maxed out your natural genetics completely after like 10 years of rigid consistency with training and diet, and you've learned how to master your physique without the use of drugs, that might be the time to consider something like that if you want to go further in the activity. To get to an easy 10% body fat, no, most definitely not.
Just furthering my opinion here that should not be on any additional drugs other than what you're prescribed by your doctor.
It really isn't that hard to do if you've got the discipline and will power to get it done. If you truly only have 6 pounds to lose, you should be able to do that in 4-6 weeks tops, naturally.
Please be sure to post back with any additional questions. Good luck!