You already maxed it from Kernel's PoV. 8GB of RAM, where 6.8GB is cache. ~700MB is resident and 459 is free because I assume Kernel wants to have some free spa

You already maxed it from Kernel's PoV. 8GB of RAM, where 6.8GB is cache. ~700MB is resident and 459 is free because I assume Kernel wants to have some free space to allocate something quite fast. 25MB swap use seems normal for a server which doesn't juggle much tasks, but works on one.