Thanks for the update! It doesn't sound like you're doing things wrong. Just struggling with a tough situation. And I've been there, mama, and I know how hard it is to do EVERYTHING you're supposed to be doing and yet not get the outcome you want. But you're doing awesome and I am so glad you're hanging in there! FTR, 6 weeks is a hard stage for everyone- there's that huge growth spurt you have to cope with and that means constant feeding even for moms with abundant supply.

First diaper out seems more or less normal (5-6 wet ones, 1-2 stool per day)...weight gain is slightly low.. Birth weight 6llb11oz, yesterday's weight 8llb 2.5oz (abt 4-5 oz in the past week)...however am still always nursing though rest in between is a bit better now.

Yet I feel like I'm not really getting this right and would appreciate any advice to my questions below:
- how do you know when baby is full/satisfied after a feed? My LO is always willing to take the breast when it is offered, whether to feed, suckle or comfort nurse.
It's so hard to KNOW when you have a young baby. Know for certain, I mean. I think that if you have offered both breasts and baby has fed actively on both and has transitioned from active nursing to relaxed comfort nursing, then she's pretty much had her fill and you can break the latch and walk away for a bit. If she's still hungry, she'll let you know.

- how to tell if baby is really hungry and want to nurse? I know I should look for rooting, sucking and my LO does these most of the time so does that mean she is constantly hungry?
Rooting and hand-sucking are great hunger cues with newborns but become less reliable as time goes on. I think the way you cope with cues that could mean hunger and might mean something else is to nurse. If she's not hungry, she won't eat. And since her weight gain has been a bit on the slow end, it won't hurt to nurse her more. Also, I'm thinking that you're going through the 6 week spurt right now, so increased feeding is to be expected.

- if baby is full/satisfied, what should they be doing between feedings? Sleep, lie around alert, something else?
Also tough to say at 6 weeks. Some 6 week old's are still super sleepy and do nothing but nap in between feedings, and some are super active and want to be up riding in a sling or in someone's arms when they aren't taking one of their few naps. Since your LO is so content in grandma's arms, and likely to startshrieking when alone in her crib, I think that might be a cue that a sling could make both your lives easier. Sling babies tend to be very happy, because babies thrive on constant physical contact, and they also may give you a little more space between nursing sessions.