HandC…...I can see that you are definitely going to go on the trip with your father...and, I do hope that you can get the good parts that you anticipate. That is totally your right...and, I can understand that you are willing to sacrifice in order to keep the status-quo of the relationship. Totally your call and your right to do so.
As I read what you share with us...I must say that all of this makes perfect sense, to me...especially, seeing as you grew up in an alcoholic family as an only child. Of course, you could be expected to be locked into this kind of dynamic with your parent. And, of course, be in treatment for low self esteem and anxiety.....this just goes with the situation...(it also suggests that your father may have done a form of what is known as "parentalizing the child")...
I am very glad to hear that you are seeing a therapist and are motivated to change for yourself.....I think that this motivation is a good sigh...
One suggestion that I, very, very sincerely make to you is this: If you haven't ever done so...please look up the organization "Adult Children of Alcoholics"...I think you more than qualify, and would benefit, enormously. It is a 12 step program.....At least, you can get the materials in the book section of Amazon.com....and read the materials....just type in the name of the organization in the book section of amazon.....
This would, of course, be in addition to your therapy....it would augment your therapy...and, give your and your therapist a ton of grist for the mill.....