I'm looking for a phrasing that will convey that this is my chosen path, those are my priorities, I do very well in life (...)
This is not about you. It is about them.
I assume their intention is to motivate you to get the degree. Their strategy (pointing out drastic future consequences) is known to not be very promising, and it really isn’t, so they do more of it.
They probably see this as their contribution to a happy life for you in their role as parents/relatives.
And your degree might even reflect positively on their social status. I think this is inherently human.
So, discussing this as if this was about you by countering their arguments etc. is feeding their attempted solution to motivate you, straining the relation even more, resulting in you avoiding them more. At the rare encounters, they then will double their efforts to work towards their noble goal.
What to do?
Consider what I wrote when they display their „motivating“ behavior, and see it as their continued attempt to do their job well, to be loyal to the wellbeing of a family member.
Steer the discussion to their motives, and really listen to them.
Bob: beggar, under the bridge ...
you care more about that degree than I do, don‘t you?
Do those worries keep you awake at night? That must be terrible, because there‘s nothing you can do about it. (absolutely no sarcasm!)
Do you say this to motivate me because I am important to you, because you want me to do well in life? And that degree means this to you?
How would my degree effect you and your life?
Would you feel elevated by having a graduated engineer in our family?
Are people bugging you because I dropped university?
Do you feel as if you failed because I dropped college?
Is it hard for you to accept what I do? ... How comes?
After really listening to what they say, you might...
what do you think moved me to do as I do?
do you think I worry more or less than you do about this issue? (...) How do you think about this?
would you like to hear how I feel about this?
do you feel the way we are talking about this is making our family meetings better or worse?
do you think your „interventions“ have rather positive or negative effects on me / us?
After listening, introduce what effects this has on you.
Whenever loyalty to your well being is spoken, honestly appreciate this:
I am glad I have a brother who cares about me, who‘d be there if I need him. Listen, in this matter, I don’t need you, I‘m really fine.
These strategies might really transform the way you relate and talk to each other.