Larne failed to take advantage of a few early mistakes by Crusaders with Andy Ryan firing off target twice after Conor McKendry had done well to dispossess defenders on separate occasions.
Philip Lowry then diverted Mark Randall's strike from a Cosgrove corner before Jordan Forsythe fired well off target at the other end.
Gary Haveron's side broke the deadlock when Cosgrove headed Ives' corner towards goal from the back post. Jarlath O'Rourke attempted to nod the danger off the line, but assistant referee Bogdan Sfirloaga adjudged that the ball had crossed the line before the interception.
Crusaders levelled the game in first-half additional time when Stewart Nixon's cross from the left wing sailed over the Larne defence and found the unmarked Blaney, whose powerful effort flew into the top of the net.
Ives leapt highest to head home Cosgrove's delivery into the box and give Larne the lead again after Gallagher had done well to recycle a half clearance and find Cosgrove on the wing.
On the 70th minute Nixon couldn't keep his effort from close range on target as the home side searched for another equaliser.
Lowry had the best chance to level the game in stoppage time, but the midfielder misjudged Jordan Owens' flick-on and fired well off target.
However, the action wasn't done there with Callacher finding the back of his own net when he tried to divert Dylan Sloan's cross into the box out of danger.