Brake pedal firm after pumping w/engine off; if on cant get

So I changed my brakes the other day. Got air in LF line, fixed that.

However, now that I understand how brakes work, I'm pretty sure when I press on the pedal it should be stiff, it definitely should not give into the floor after continued pressure...right?

Scion TC 2006, has ABS.
My guess is I need to bleed the master cylinder, because when I pump the pedal with engine off, after 1 pump it becomes very stiff, and stays stiff...means lines are good?

But, when I pump the pedal with the engine on, I hit some firmness, but if I maintain pressure, the pedal gives on down to the floor.
I wasn't able the bleed the other lines (couldn't untighten them), however I think they're good because yesterday when I had air in the LF line, the pedal would give to the floor both engine on and off. sounds like the lf brake hose was disconnected and the fluid ran out? if so did the master cylinder run dry?

if the master was empty, u need to bleed it, and then bleed all 4 wheels. if the bleeder screws aint cooperating, spray some pb blaster on them and use a flare or 'line' wrench to loosen them without rounding them off:

Front hose wasn't disconnected, just the bolt on the line loosened a little bit while I tried to push the piston back into the cylinder, thought having the line disconnected might make it easier. In the process I heard some gargling-- like air was getting in a little. Wasn't terribly much I think. Anyways that didn't work so I ran to Home Depot and got a C-whatever they're called and pushed it back in...air might have gone, too, but judging by the firmness of the peddle now with engine off I believe I got that out from the line.

Come to think of it driving today it didn't feel very bad at all or any different from before-- I'd just like it to be tighter.Car Repair Talk's forum.