Based on your activity level, you could probably up your protein intake. You could use a very low carb protein powder if you are not comfortable with eating more solid protein foods or the expense of it. And see how it goes. How does it affect your bg levels etc. Adding muscle mass takes time. You could drink it before getting on the bike or after it, or during etc. Depends on how long you are riding for. Mix it with water, add some sweetener if need be. Just read the label to see what's in it. Many are full of ****.
Weights are good, but if you don't enjoy it, you won't stick with it long term and if you are already very active and enjoy what you are doing now and that takes up most of your time, then perhaps adding more intense exercise is not the answer. That's up to you. I'd say 2 or 3 times a week would be enough if you wanted to try it. You have to allow time to recover, the older you get, the more recovery time you need imo, based on my own experience with it.
I do think you need to eat more, that's what it comes down to. I'm in the same boat. You have to find a balance with what keeps bg levels where you want them and be able to eat enough on LCHF. Personally, I have decreased the fat content and increased the protein. That has stopped my weight dropping and have gained a few kgs and maintaining. Still need to gain more, but it's a slow process. And a case of re-adjusting once you plateau for some period of time.
Good luck with whatever you do.