I grew in a family that speaks Wu Chinese, so I cannot differentiate between the "ing" sound and the "in" sound. Are there any ways to tell them apart or pronounce them differently? They sound the same to me. (Hanyupinyin)
The difference between "in" and "ing" is in the ending sound. Say "in", hold it for a second or two, and feel the position of your tongue. Your tongue should be in the front, touching the roof of your mouth just behind your front teeth. Then say "ing", and do the same. Your tongue should be at the back of your mouth. Try to hear the difference in sound when you do this exercise. Differentiating the sound will come with practice. Hope this helps.
Many people in South China are not clear of n and ng. That's, as you mentioned, Wu ascent problem. I suggest you use dictionary to know what character are n or ng, and listen to those who pronounce good, for example, presenters of CCTV news