Incident at my local regionals (asking for advice on what I should do moving forward)

Just wrapped up my debut tournament at my local BO-1 regionals in Singapore. However, there was an altercation that I was a part of that I would like the community's opinion on:

I was playing RB/Ogerpon against a Dragapult deck. The first prize card from either side was taken past the halfway mark of the match. I had managed to avoid Dragapult's KOs by shifting my Pokemon around. As such, this left 4 prize cards on both sides around the 5-10 minute remaining mark. Opp said that 'we have to go faster' - however he still played at his usual speed. At no point did I intentionally stall, my turns took a reasonable amount of time.

When the timer ran out, a nearby judge observed that we were still playing and told us to end the game in 2 turns (opp's turn at the point of calling, my turn, game ends). Opp was not able to attack me and I chose a hail mary by trying to generate energy on my Ogerpon to KO his Dragapult. However, it failed. During opp's turn, I had clarified with the judge that the game ends on my next turn. However, opp proceeded to switch out his Pokemon after the game ended and told me that I was KO'ed. I then clarified with the judge again and he said that it would count as a double-loss for both players (official ruling, no exceptions). Opp then proceeded to log the results on his phone and showed it to me - for some reason he indicated it was a game win for him, and a game loss for me. I then clarified with the judge that it was a double loss, but the judge then told me I had the option to concede. Opp then asked me if I wanted to concede. After thought, I decided not to, to his ire. He stormed off saying that I should have given him the win as he was about to win.

Feeling guilty I confided in multiple players after leaving the table about the guilt from my choice to not concede. All of them (more skilled and experienced than I am) told me that I was in the right to have my choice to pick a double game loss. Moreover, they told me that I was being gaslit and bullied by opp, and the judge should not have allowed me to make a decision in the first place, as 1) I should concede on my own terms, 2) it should have been done before the game ended/officially I cannot concede past the timer, 3) opp should not have a say in asking me to concede. They told me that I should have reported opp for unsportsmanlike behaviour and referred the judge to head judge for his ruling.

What should I do moving forward in future scenarios? I did not report both opp and judge at the venue as I was still paralyzed by the stress and turn of events.