That's typically the way I do it as well although I've found that to guarantee enough rep to get the support of all 4 guilds before day 14 you need to change from the easy quests to the medium ones. Maybe at high charm affinity you could get away with 2 easy quests per guild but at low charm affinity it's not enough.I haven't tested it that much in the current version, but in the previous version at about 80-90 wits picklocking was basically guaranteed to succeed. Maybe it has changed in the current version? As to the loot, the amounts generally aren't all that amazing. It can be a good way to equip your slaves at the start of the game, but later on it kinda stops being all that relevant. Although, that's more of a criticism of the current state of dungeons as a whole.
I've found that focusing on quests is the best way to beat the debt. Do the first 4 quests -> buy more quests upgrades from the quild -> do the 8 new quests -> have enough rep to get the guild election support quest -> finish the election support quest before the 14th day -> never pay a dime of debt. At least that's the theory. I've been too busy messing with the game files. It does require decent charm factor from the master, but I've gotten the election support quest on the 7th day so it should be doable. You'll need to buy some stuff from the store to complete quests and need to get a bit lucky with quest conditions, however.