Thanks for all your responses. It's really helpful to get other perspectives.
My personal goal is to loose body fat. I wouldn't mind toning up and gaining muscle as a bonus, but really, I just want to slim down overall.
it sounds like you are trying to do 2 things at once - very difficult imo - i think to both gain significant muscle and lose significant fat your diet and workouts have to be totally dialed in and consistent
your workouts and diet seem to be geared towards losing fat - not gaining muscle - although a few people might make gains on a perfected diet while losing fat, the more common method you'll find is that people slightly overeat in order to gain muscle and ensure they have adequate calories, fat, and protein to build muscle - very hard to lose fat if you are slightly overeating
also exercises for muscle gain are the big classic HEAVY lifts - everything with freeweights - deadlifts, squats, presses etc. HEAVY weights so that reps go no higher than a dozen, but even better is to stay below 8, the reps stay low not because you quit at 8, but because the weight is so heavy you can't do any more - it is my belief that the last one or two reps before failure stimulate most of the muscle growth - these lifts combined with slight overeating is the classic, standard way bbers pack on muscle - and many/most bbers don't do any cardio at all when they are bulking up.
"Basically it's hard ass weight training to full muscle fatigue. It hurts like a mofo. screaming is not unusual. I do leg presses, leg curls, compound row, chest presses, and some kind of ab workout with no rest to speak of for 20 minutes twice a week."
I don't understand how you can fully work a muscle when there's no rest - not to say this isn't a valid training method - just that i don't understand it. If i don't pause for 60 or 90 seconds between sets or exercise, whatever i do next will be diminished. For instance, if i'm bench pressing to failure i'm exhausted after my last rep, and if i jump right into curls i'll do less reps than if i had waited 90 seconds. Sometimes on my last set i'll go to failure, and with no rest drop 10lbs, go to failure again, and repeat that 3 or 4 times, and i get an insane pump from it, but that's not switching exercises, it's just overpumping one muscle group. then i fully rest before i hit the next group.
I also question the testing methods
"I have lost some fat too. I'm about 4 lbs lighter overall from where I started."
as chrisjs has already said - if you've only lost 4lbs I don't understand how anything can be tested with any sort of accuracy. how much of that 4lbs is fat loss? how much is LBM? how much is water? not to be crude, but 4lbs is not much more than a few glasses of water and a bowel movement - hydration levels alone can account for 4lbs of water in 24 hours.
my advice would be to not worry too much about losing LBM, and to focus on fat loss - while consistent and accurate testing methods are possible, an increase in strength over time has always been my best measure, but that also assumes consistent training and performing exercises in a normal way with adequate rest between sets - sure sometimes strength will go up and down a tiny bit, but over time it should always increase or at least maintain - if you're getting weaker, then it's time to make adjustments