Even with only 150 entrants you still should be having a 100buy-in BR so to play the $30-$60 you need $3k and $6k respectively. This might sound redic but seriously, you need more buy-ins, you got lucky if I'm honest unless you have been continually reloading to fund $30/$60 games I'm unsure as to how much your roll was to start with? I'm not sure of your roll, but because it sounds like it's massive increase in your roll, as you said it's "20 buy-ins" - what was you playing with before that?
Even if the games are the softest, rest assured you are going to encounter prolonged periods of not cashing so be prepared to move down if you wish to continue playing $30-$60's. I'd personally be playing a maximum of $20.00 games with the roll and amount of players involved. Hell you only have 30 buy-ins for STT at the $30 level and only 15buy-ins at the $60 games and it's not uncommon for the very best of players go on swings of 20+ games.
Good job on the cashes by the way, keep up the good work.
Personally though in my opinion what I would do if I was you is drop to $10.00 MTT's and go from there, you will never go broke even if it's a much longer grind.