Would a prayer request by someone who is selfishly, possessively, clinging to a suffering loved one who needs to transition be safely ignored by Creator in the dying person’s best interest?

Yes, this is so. Prayers are answered in proportion to the need, and in proportion to the intention, and in proportion to the level of belief of both giver and recipient. There are as many ways of compensating as there are variables in the equation. All is taken into account, and someone who is genuine and reaching out from their heart may have tremendous power on their own to turn things around for a fellow human, but the step must be taken, and their role must be genuine to have an impact. This is the capability of all divine humans, to be an agent for change and an effective advocate to recruit divine help.