For me, it's not a wise idea. No matter how pressing it is for me to prove to a friend how successful I have been in Bitcoin, it won't get to the point of showing my accumulation.
I understand the level of happiness and excitement that OP has to see an old friend after so many years. And this has made them to go into a serious discussion that led them to share their experiences and how they are surviving since they are of age now. Am trying to relate it to my own experience. Perhaps OP's friend has shared how own experiences and what he does to make money over there, that is why OP feels the need to share his own as well and he took it extreme that he almost told his friend how much he had in his bitcoin portfolio.
Although, it is not advisable to allow happiness to make us unleash our identities. There are things we keep privately, and our Bitcoin portfolio is one of those things. Influence of drugs and alcohol can make us say things we don't want to say. That is why avoid them so i won't make mistake i would regret later.
Now i am not saying i do not trust my friend. But if had a friend like OP, i won't tell him what i have in portfolio. This is because his said friend had been away for a long time and so he might have change positively or negatively of which it will take some time for me to build trust back. Since i do not know his current behavior and character ever since he left. I will study him first before i can disclose little about myself. Yes, i can teach him bitcoin if he is interested but i won't show him portfolio to prove any point.
Although it's hard to convince some people to do something these days, you have to show them that you have benefited from it. Well, I'm not a party to introducing my friends to Bitcoin yet until I am well acquainted with Bitcoin knowledge. Though I have been here and have learned a little, it's still not enough.
Your right, people prefer testimonials to believe you are telling the truth and also to prove that a particular system works. Most of these testimonials are fake and framed up but since they have seen that they will believe. This is the same reason why i always conclude that to lure someone to do something is so easy all you have to do is to prove to the person. Individuals with lack of information's and exploration to digital society can be easily deceived to do anything the i introduced them to on the internet. as long as you show them some successful pictures to convince them. And that is why so many of them fall for scams.
A better way to teach or share Bitcoin knowledge to a friend or relative is to show them how it works, provide video and documented resources for them to learn, provide FAQs for them so that they can understand while learning. Now this strategy would make them to have conviction on their own. So that when they start, they will be a true believer and not someone who was convinced because of the success stories and promises showed to them.