Pour over coffee is too bland or too acid I buy coffee from local roaster and when I make it in two mins, pour over with v60, it gets too acid. If I make it in 2:45 it gets too bland. My other settings are the same.

3 seconds off boil. 17-18 grams coffee per 250ml of water. Washed filter, pre infused for 40 seconds, dripped in spiral form. 

I fear that the roaster is not worth the effort but it's the only local roaster I know. They leave the roasted coffee in a pot for 2 days and they put it in a bag with valve only when you buy it.

What should I try to give this coffee a chance?
It sounds like the main thing you're not carefully controlling for is temperature.  I have found that if I use cooler temperatures (80-92 degrees celsius) for my pour-over, I get very bright/acidic tones.  Hotter water (92-100 degrees celsius) always gives me more bitterness and earthy flavors.  I use an electric kettle with a thermometer to maintain the temperature accurately so I can keep a temperature in the middle, in order to get both sets of flavors.  I would guess that by 2:45, your water is too cool and you're just extracting the acidic notes.  Try keeping your water hotter (and measure to see what temperature you're using).  

I might also suggest giving your coffee a nice 60 second bloom time (pour enough water over them to get them wet, then wait for the gas to escape).  That helps you extract everything (complex and bitter notes included) from the grounds.

You could also consider letting your coffee age a bit longer.  Sometimes, beans are best 7+ days after roasting.

Good luck!