pressurized co2 questions

i currently have the red sea co2 setup (yeast), with a venturri to
disperse the bubbles. i want to move to a pressurized co2 system. if i
connect the venturri to the pressurized system, do i still need a bubble
counter? ie: do they both do the same thing for me?

when my filter is off, the bubbles from co2 collect at the surface of
the water, but do not pop. with the bubbles sitting there, is the water
obtaining co2? in other words, if the bubbles rise to the surface and
pop, as when my filter is on, am i getting less co2 into the water?

ive read many DIY articles which state you can get a 10lb tank for
$35-40. i called around today to many shops and the cheapest i found a
10lb tank was for 93$. what is everyone elses experience with this?

also can someone point me to where i should order a gauge from? or a
brand, etc. thanks