The 34-year-old Forsström was one stroke ahead of Belgium’s Thomas Detry overnight, but Dantorp’s late charge from third proved the main threat.
Forsström did just enough with some late birdies for a 2-under 69 to finish 17-under overall as Dantorp posted 67 to end on 16 under.
“I’m very happy, I don’t have any words,” Forsström said. “I just thought to give myself chances and hopefully some would drop.”
Dane Thorbjørn Olesen (66) finished two shots behind Dantorp in third place.
The No. 429-ranked Forsström came through qualifying school at the end of last year to gain his tour card.
“It means everything to me to finally make it. I was happy being out here after Q School,” he said. “I’m super happy with the win and I proved to myself that I can win out here.”
Detry (73) dropped back to a share of seventh place.