I assume you mean 6.5 km or 6.5 miles (not meters)... right?
In either case, I think you'd be safe to offer a 20 Mbps plan to this customer. The sector capacity is dependent on how much data is actually used, not the plan they are allowed. So, if you think this customer would consume the maximum bandwidth they are allowed all the time, it may be slightly riskier, but in my opinion, I would allow this.
From the screens you've provided, it looks like this SM is in 6X modulation most of the time, so he's doing fairly well, and the overall sector capacity (if ALL SMs are in 6x modulation) would be about 95 Mbps. If you factor an oversubscription rate into that total capacity, you can estimate approximately how many subscribers you can adequately service at various package speeds.
There's a very old (but still pertinent) discussion here, and another much more recent discussion here.
A good reference for the impact to the sector is the knowledge base article on the shared sector capacity concept here.
I hope these links are helpful.