Dear Marcoen,
You defended your point very well, using the artillery of critical thinking, and I agree that we can be certain about very little. I can't name one thing about we can have absolute certainty. The Higgs boson is not singular in this respect. One can't be sure that the sun will rise tomorrow, or that it even raised this morning. Or even that there is a sun! When we look on the window, we assume that the world will be there, but what makes us so sure? We can never have absolute certainty. So I must say that I agree with you, and not only in the case of the Higgs boson. How people deal with this uncertainty? They had to learn to deal with it, because there are not few the situations when a fast decision, even wrong, is better than indecision. While we were living in the wilderness, often running or attacking were better options than carefully analyzing what to do. People learned to justify their choices, so that they can run or attack without hesitating. Very often people feel very certain about their opinions in politics, religion, science, UFOs, etc., and maybe the explanation is that we can't do anything if we doubt of each of our steps, so we learned to believe in our choices. Toddlers can't learn to walk if they wait to gain certainty that at the next step they will not fall, so believing is doing.
So people learned to make bets, and justify them, for the peace of their souls. Anything is a bet, and the explanations around it are justifications of the choices made while betting. We bet that the Sun will rise tomorrow. We even bet that the universe will still exist. We bet, so that we find a reason to earn our food for tomorrow, to send the children to school, to have health insurance etc. And if we will see the sun rising, as you pointed out, we merely observe the photons. Or are we even sure that we observe photons?
Science is full of bets too, and it is in the spirit of science to acknowledge that and never forget it.
The existence of the Higgs boson is just a bet, and the odds that a particle with properties that can be assigned to Higgs was find are given by the 5 sigma. The odds are probably much greater, if we remember that the Standard Model, which needs the Higgs boson, explains so many phenomena, and makes prediction with so big accuracy. But, there is no absolute certainty.
Best regards,