I would do a TRT dose like others have said, 180-210mg per week.
You are very tall like me (I'm 6' 6"). I am going to guess you are not as wide in the shoulders. When I was 280-290, I was at most 15% body fat. I'm 250, 8% BF now.
I think you could reasonably be 250 and under 15% BF with the right diet and training. Even at your height, 240 would look really good especially if you got the BF down to the 12% range. The 200 of Test would help you hold muscle while losing the next 30-40 lbs.
Most personal trainers suck, especially at chain gyms (Planet Shitness, Anytime Fitness, 24 Hr Fitness). Honestly, you could probably get a better training and diet program on YouTube and that is free. Greg Doucette may be annoying but he is knowledgeable.
The fact that you lost 70 lbs. already is huge. You already did the hardest part, now its just fine tuning. One suggestion as far as cardio. Throw in some boxing. It doesn't have to be with a heavy bag. Sometimes at home, I put 5 lb each ankle weights around my wrist and shadow box for 30 minutes. Not only does it burn a pile of calories but it adds muscle. Again, you can learn the simplest boxing punches with a YouTube tutorial.
Good luck to you. Remember, no one looks better than a tall, jacked guy. There are tons of short, muscular guys out there but very few 6' 4" and above. Those are the guys that turn heads.