Marijuana use and job/grant opportunities
Regardless of current policy, your career may be affected by policies 30 years in the future. Although the trend seems to be towards increased tolerance of marijuana, it is not possible to predict how things will be throughout your career. When I was a teenager US federal policy seemed to be moving in the direction of eliminating poverty and racial injustice as important objectives - see the "Great Society" programs. 

You seem to be in a field that may lead to US government employment, or needing a US security clearance, or both. That makes you very vulnerable to changes in policy. The consequences of not being able to truthfully deny ever using illegal drugs could change in either direction.

You will have to make your own trade-off, but remember that you need to consider what could happen over several decades, not just what is happening now.