How long before a parent failing to show up for visitation is considered child abandonment?

On the facts you present in your question, and subject to the terms of any existing court order or judgment or agreement, it would seem that generally, you'd be likely to prevail on a petition to relocate, provided that the location you are moving to would result in your obtaining a better job or better wage, and/or has better schools and opportunities for your son, and/or would put you both closer to relatives and family that would be in a position to assist or help you with child-raising, financial and/or emotional support, etc. Florida has a relocation statute that is generally strictly enforced, so you must be certain to comply with it. Consul with an attorney to discuss the specifics of your situation and your options.

It is not considered abandonment. You are asking the wrong question. But then I cannot decipher what the right question might be.