Stanger'66- Don't worry about not eating clean all the time...keeping this stuff reasonable is how you can make it work long-term. Heh heh, I myself just got home from a big Denny's breakfast
I don't worry about catching up or otherwise doing anything special when I miss/overdo a meal, I think more long-term than that and in ten years it'll never matter
See how the other legcurl machines work for you. I never got the weird feeling in my feet
I'm trying to think of how the blood flow goes into the feet (I'd probably have to check my anatomy book) but I wouldn't *expect* it to be a matter of cutting off the blood supply. Probably more a case of pinching a nerve or something like that. As you develop your calves this might resolve itself (note that you need to do both standing and seated calf raises, each works a different part of the lower leg).
Romanian deadlifts are kinda like straight/stiff-legged deads except that you flex the knees a little bit. Think of it as a kinda loose-style stiff-legged dead.
Keep an arch in your back, really *lock it in* so you don't strain your lower back. Get a slight bend in your knees, just enough that you're not quite keeping your legs straight. Lower the bar down by bending at the waist until you feel the stretch in your hams and then go back up- you should feel the stress shift from your hams to your glutes. At the top you might want to straighten out a bit at the knees, but don't make it a big deal where you're doing some complicated stuff with a lot of shifting your body around. You should *NOT* feel a lot of stress in your lower back, but you will feel a bit.
To keep the stress on your back minimal, keep the weight close to the centerline of your body: with a barbell, keep it close to (or even touching) your shins and thighs; with dumbbells, hold them at your sides and try to keep them from swinging too far forward or back.
It's important that you keep your back "tight" so you don't turn this into a lower back-stressing exercise. As you can probably imagine, it's a kinda fine line here since you're bending at the lower back! Use a light weight and feel how the stresses shift and keep the "hams and glutes" target in mind.
Don't try to lower the bar too far down. In time you'll get more flexible and you'll be able to lower the bar lower, but if you try to overdo this you'll probably end up rounding your back to get the bar down lower and that'll put you at risk of a back injury. I think you'll find that some very light/easy work will result in significant delayed-onset muscle soreness, so don't worry if it seems like you didn't do anything productive.
If you do the Romanian deads with an olympic bar, try it with just the bare (~45 lbs) bar. If you do it with dumbbells, try it with something really light like a pair of 20s. I know, that's hardly anything, but you'll get the groove of the movement figured out and just the unusual stretching will probably make you a little sore the next day. Keep the reps around 15-20 while you're learing the movement and then, when you're using heavier weight, try to keep them below 15.
Your ab work sounds fine. My ultra-low-rep work was just what worked for me when I was younger. Keep an eye on your abs and try to feel them working; getting the lowermost portion of the abs involved is usually the biggest challenge.