Your stats are just average. They could be much better. Talk to your lineman and ask for a cleaner line with minimum number of joints. If possible ask him for a fresh line. Use this for reference.
More importantly, your attainable line rate is 6016 which is why your max speed doesn't go above 4-5 Mbps. Since November 2017 the minimum speed has been assigned as 8/10 Mbps. The line rate should be close to 10,000 kbps or above for enjoying the assigned speeds. Talk to your JTO/tell exchange officers and inquire about the reason why your line rate is still 6016 kbps. Ask them to set it higher, but do that only after getting your cable fixed.
one thing you can do is to register a complaint saying you are not getting the speed as you should get in your plan. they may check your connection from the exchange and might say the line seems ok , then tell them about the low snr margin your are getting.