You might mean 25mg/50mg/100mg?
I can't imagine doing more than 100mg, but definitely ask your doctor.
If you have weight to lose, or have cholesterol numbers that can be tweaked by diet, you really need to work on those. When I was 30 pounds heavier, in my early 50s, I couldn't keep a boner to save my life.
Your LDL should be below 70, and your HDL above 40.
Exercise helps.
Yes, talk to your doctor, including a urologist. You might be a candidate for Tri-Mix injections.
Definitely try a cock ring, and you can get an assortment of silicone ones with "grab handles" for not too much money. Try different sizes. Install it once you get hard, but don't leave it on for more than 30 minutes. Your penis will swell up a bit, highlighting the veins and the head, and it can improve sensation as mentioned by another poster here. It's kinda cool to at least try it for variety. It's not guaranteed, but can help. I've used it on occasion and my girl likes it and can feel the difference.
Cialis, even 20mg, does not do much for me, but I do take 5mg daily for BPH to reduce the number of times I get up at night. It may, however, work for you.
Good luck!