One espresso has ~60mg of caffeine, which means a Fistbumping Lesbian has 7 * 60mg = 420mg. This means it's 20mg over the FDA's determination of what's safe for adults, so in the range of the lemonades from the article linked above. Don't drink more than one of these per day.
As someone who suffered from severe chronic insomnia for 14 years, there were times I'd drink 5-6 rockstars (800-960mg) to make it through my 12 hour shifts. No one should ever do this, obviously, but when you haven't slept in days you do what you must.
No, and it doesn't sound tasty. If it's a 250ml mug (roughly a US cup; exactly AU/NZ cup) though, its caffeine content should be lower: 80mg from the energy drink, 40mg from the mate, 100mg from the coffee = 220mg caffeine.
It's definitely this. Most coffee shop coffee is espresso with or without other stuff added in, like steamed milk if it's a latte. A shot of espresso is essentially one cup of it (as in an espresso cup, not the kind of cup you'd measure flour in when baking). It actually is a similar volume to a shot of vodka though
A mug of drip coffee has about twice as much caffeine as an espresso (depending on your beans, extraction, and how big your mug is). So this is still like drinking three and a half mugs of drip coffee at once