The wiki says Strong (and I have noticed that Curie and Hancock as well) likes to be out and kill things... And that gains approval even if it does not seem that way. Allow me to elaborate; you can get strong to adore/idolize you simply by going out, exploring and killing. So you do not necessarily need to do things your companion "loves" or "likes" for him to gain approval. I can confirm this is true for Curie and many people seem to agree it works for Strong too.
So my suggestion? Go to Diamond City, check the bounty board (that's left to the guy selling "swatters") and do a lot of them with him. Most bountys just requiere you to go somewhere, kill the boss of the place and loot. So do that, but remember never to lockpick.
What I am trying to say, is that the following is without logic, but still happens: I left Codsworth at Sanctuary, and you notice that he "loves" when you customize a weapon or an armor, and so I intentionally only customize things at Sanctuary to have him "loving" it, but how can it be that it took me 8 "loves" just to reach the first level of approval, and with Curie i have barely got one love and 4 likes and she is already in 3rd level of approval with my character? Well it seems that "hanging out" and "watching each other's back" raise approval silently. So you most definetelly want to take strong with you to some raider camps and gunner strongholds. He will "approve" just being there as a team teamwork. I hope someone with PC and console commands may explain how does this works (because it does) in terms of how much time spent, or xp gained, or enemies killed it takes to get "likes" equivalent approval... But that's that.
If you have trouble finding the bounty board, go to the mayor's office and ask the secretary for work. The bounty board will appear on your map after that.
The Molecular Level quest both is and isn't a point of no return, fundamentally it requires you to make a choice - what you do need to consider is that speaking to a faction will provide you the infiltration quest for the Institute but also make the equivalent quest for the other factions unavailable. It is possible to reconnect with the factions you didn't choose after completing Institutionalized though.
The game is seemingly inconsistent in warning you when you're about to make permanent changes to your faction reputations. The actual point of no return varies by faction alignment.
In the case of the Institute quest line, speaking to Allie to start the Mass Fusion quest will pop up a nice warning stating you're about to become permanently hostile to the Brotherhood of Steel. There isn't a subsequent warning when you do the same to the Railroad, you'll just get lots of failed quest spam if you've got quests outstanding but in fairness, the mission is specifically to kill the Railroad so...
For the Railroad, I believe the switch occurs silently at the start of the quest Precipice of War. I definitely didn't receive a message and the conversation to start Precipice of War seemed to flow continually from the conversation that ended Operation Ticonderoga - the Brotherhood of Steel just stormed in and then I got lots of quest failure spam.
For the Brotherhood of Steel, the mission that makes you hostile with the Railroad is Tactical Thinking.
Best Answer
The vast majority of companions do not have quests which are required to get a perk. You simply need to max out your reputation.
The exceptions are MacCready, Curie, Cait, and Nick Valentine. You'll need to complete each of their quests to receive their respective perks. While the quests are only offered when you reach maximum affinity, it's possible for affinity to decline between when you are offered the quest, and when you complete it, which means you might not get the perk immediately upon completion of the quest, as both requirements must be fulfilled simultaneously. Simply butter them up a little bit once more to get back to max affinity, and you'll gain the perk.