Thank you for your question
My name is Clare and I shall try and give some practical assistance
Custody - Sole or Otherwise is not a word that has been used by the Courts since 1989 when is was replaced by the words "Residence and Contact" to represent which parent the child actually lives with and what time he or she spends with the other parents.
In turn these words were replaced two years ago with the word "Child Arrangement Order" to indicate that the child remains the responsibility of both parents - although they may spend more time with one than another.
There is NO automatic right to have any time with a child - let alone 50% of the child's time.
It is the right of a child to see both parents and the courts will enforce this if necessary
The priority is the needs of the child - which is for a routine of contact that works for the child AND both parents
Last minute weekends with long distance travel is not reasonable - and travel should be shared - with you taking on slightly more than half if you are the one who moved away
If your ex continues to threaten then offer to discuss matters using Family mediation
if that fails then offer a pattern of contact that fits with the child's needs and is a reasonable compromise with your ex's work and say that if he does not want that then court is the only option.
Please ask if you need further details