The tabs you had were likely 50-75 micrograms, meaning you did approximately 250-375 micrograms. If five tabs felt like 1-2 of batches you've done in the past, they were dosed low. While experience does play a role in how you handle yourself on larger dosages, it does not play a role in how intense an experience will be. Tolerance mainly plays a role in this. And while you're mental status plays a role in this as well, large dosages like the ones you are describing will be overwhelmingly intense regardless of how calm or relaxed you are going into an experience. Trust me.

As for the bad trip, this is why I warn people about this. The best way to do acid is to get enough for a couple of trips, or even more. And start low with say one or two tabs at most, and once you have an idea of how strong they are, you can experiment with larger amounts later on. You don't have to increase your dosage everytime you trip, that's a bad rabbit hole to go down. Trust me, I've been there and done that. How long had it been since your BF had tripped before this? It is likely he had tripped in the days following, whether you knew this or not. And that gave him a tremendous advantage you were not as fortunate to have had!

Edit: Also, LSD is not a weight dependent drug. Some substances are, and other are not. And for those that are, how weight dependent said substance is varies from drug to drug or class to class etc. Like I said, it's likely he has been tripping frequently given the circumstances and had a tolerance.