Bava Batra 145: Wedding Presents

What happens to gifts that are given in advance for an upcoming wedding, and then either bride or groom dies? (or perhaps less dramatically, if wedding is called off for other reasons - but the Gemara's case is death). Plus, what about returning bridal gifts - the kiddushin money, for example. Also, on the groom/groomsmen gifts - the reciprocity is presumed for each wedding, but that also depends on the location of the groom in his expected presence at his groomsmen's weddings, for example. Plus, different kinds of scholars of Torah - with their various strengths and skills.