If belief quotient in the divine is less than 100%, does that increase the likelihood of a low level spirit communicating through a Ghost Box? Will talking with an earthbound spirit significantly increase the likelihood of spirit possession?

This scenario is very likely to happen. As you know, any outreach beyond the self through your consciousness will be answered. If it is not answerable by a divine level being because of circumstances, as we have described in terms of potential limitations on the part of the requester, some being or consciousness will answer because the interlopers are always looking for victims and will engage with someone who is reaching out to the beyond with the hope of establishing communication and trust from their side, and this will create a lowering of their barrier to an external source of energy and will indeed likely lead to spirit possession. All such outreaches, including meditation alone, need to be done with a prayer for high-level protection by the divine to keep the requester safe. This, too, has the same standard for any divine outreach, that to be enacted must be launched with clear intention and belief in the divine and in the self being worthy, for protection to be granted. This is why such enterprises carry risk and is yet another example of why people need to spend significant effort cultivating their belief and their confidence in their own spiritual standing with the divine—that is the best preparation. Simply buying an adjunct like a Ghost Box does nothing to address these major factors governing success of the enterprise, and for it to happen without risk.