Those numbers look normal to me. ONLY the sequential speeds are going to be fast, and yours are. The others, which are either high queue depth or random access speeds, are always slow for NVME drives which is why other options like Optane are gaining popularity (At least for the type of hardware, not necessarily for the Optane brand or form factor) because they have much higher speeds when it comes to random operations.
I don't know where you got the idea that temps are ok at 68 degrees either, but most NVME PCI drives start throttling at about 60°C. 70°C max, on some models. The NAND operates best at 40°C while the controller usually is too hot above 60. Heatsinks that do not include a fan, have been typically proven to not only not be helpful because they sit on the NAND which you WANT to be warm, and not on the controller which is what you want to cool, but to actually make the problem WORSE. A home brewed fan might be a lot more helpful. Even my 970 EVO which has greatly improved performance and has fixed a lot of the heat issues that plagued previous M.2 NVME drives, still has issues with throttling and I have had to home brew a cooling solution for it. It's not pretty, but it's temporary, and I'm planning to build a more more aesthetically appealing mounting solution in the near future.
You will probably need to custom tailor the fan profile if possible so that the NAND stays as close to 40°C as possible (Usually temp 1 on most NVME drive sensors) and below 60°C (Could be different for your drive. Need to find the exact specifications of your throttle temp).