You have stated that you have a custody agreement. My response will be tailored to that fact and would be different if you had a consent order (where a judge has adopted your agreement as a ruling of the court). Your and your ex-wife's relative abilities to provide for your child's stability will be relevant factors for obtaining an initial child custody determination, In addition to the stable home that you can and do provide for your child, you have deacribed a parental history (in terms of time-aharing) that demonstrates your ability to care for your child over an extended time period. You already have, in effect, shared custody of your child. Each factor you have listed is quite relevant to a court's ultimate task of placing your child in a court ordered arrangement that promotes your child's best interests. If you are the person who initiates the action, you may be able to convert your shared custody arrangement into your having primary custody by court order. If your ex-wife's drinking problems are extreme, you may also be able to limit her to having supervised visitation.