Is it helpful to stay single if I am not going to become a monk?
What matters is what you do when you are single. If being single means using prostitutes to satisfy one's sensual desires, it could lead one further away from the path as compared to a person who restrains himself to one woman and practices loyalty, kindness, doing good deeds together etc. 

But if being single means being celibate and using one's free time for meditation etc., one would generally have a higher chance of progressing in the path as compared to the average family man. 

In the time of the Buddha, there were monks who went to forest for seclusion and ended up having sex with monkeys. So what really matters is what you do when you are single.