I just skimmed the other thread, but you need to realize that three days of poker and $400 at 4/8 is really just a drop in the bucket. Losing 50bb is common, every single poster on this forum has these downswings many times over in their lifetime.
I would reccomend reading some books and this forum to get a better understanding of poker(variance and bankroll especially) because no offense it doesn't sound like you really understand it at all.
Once you've done that you could probably start with very little online and do quite well.
I know the below link is a little old, but the content is what is useful, you may have to research a bit in case it's not up to date, but it gets the point across.
building a bankroll