Are you really having a massive problem with Tantrum spirals still? The seem to be much harder to trigger now. Or maybe I've just stopped killing dwarves in random ways in large quantities? I certainly don't accidentally on purpose flood my fortress anymore. I've stopped letting mountain gnomes nick my booze all at one time. The tree's are not bombing us anymore, so your planter shouldn't just be randomly killed. Training is so awesome now that danger rooms arn't even worth the risk of injury.
I find roasts, grand dining rooms and individual rooms tend to make dwarves pretty happy. Access to clean water means you don't lose injured dwarves to dehydration. And keep'em busy. Busy dwarves are not socializing and making friends, but they are ALSO gaining skills which will allow you to generate happiness(through more masterwork tables and statues and chairs and beds) in some way. The more happiness your dorfs have, the less stress they will feel, and you can normalize them.
Also, Military training. Wanna prevent tantrums? Keep as many dwarves as possible under orders. They gain skills and attributes rapidly. They don't just become better fighters, they will become better socializers(I think it's through attribute and observer gain). Lots of indimidation, but lots of conversationalist, consoler, comedian, etc. It's the best thing a dwarf can do if he's not making valuable goods.
Unlike earlier versions where military training was slow and tedious, currently, it's amazing. After 6 months, your dwarves will be stronger, faster, tougher, better fighters and more disciplined. They will have gained ranks in student and teacher. I don't know what the advantage of Teacher and Student are, but dwarves with higher levels of student seem to pick up skills rapidly. I wonder if that's why they are generally better with social skills? They have a bonus to skill gain from student, so they hit higher levels quicker?
I think rotating dwarves in and out of the military is probably where it is at for preventing tantrums. While the dwarves are training, they will be gaining skills and attributes that will help in the fortress(strong, fast, hard to tire stone haulers? Sounds amazing!), which will allow you to keep more dwarves happier. They should also acquire good social atrributes, which should help them trigger happy thoughts in other dwarves more often. They should have a higher threshold to bad stuff happening, as well as less exposure(if they train in a barracks, they arn't getting horrified going to the refuse stockpile) to bad stuff, except when REALLY bad stuff happens.
Say, this would be a theoretical set up: 70 dwarves, 50 of them are in the military and training. 16 of them are year-round soldiers: if they take a break from training, they are stationed or defending a burrow. Or pump operating. But training is my favorite. 24 of them are in 6 man squads, set to 3 months training, 9 off. Or 4/8.
My biggest fear is the combat drill thing. Turns out that dwarves love to do combat drill. They absolutely love to do it, even if they're not active. I sometimes fear that you could end up with military dwarves who do lots of drills, and don't do a lot of hauling. IF it works well with skilled crafts, then you could do some cool things with having your entire fort cycle through military training: after four years of that, those dwarfs would be bad mama-jammas, and problably extremely resistant to tantrums.