If it's a slow leak then I wonder if it leaks when hot--in which case any oil (which thins under heat) is going to leak.
In hot 'ole Florida I wonder if you are fine with a HM 10W30 and call it a day. 5W20 is fine I'd think (originally spec'd, no?), not sure you need a 40, but it isn't hurting anything, but I don't see why you'd need a 0W at all, unless if the particular oil has other properties that you want and that's what it is.
2011 Toyota Camry, base, 2.5L/6MT, 203k, hers
2010 Toyota Tundra DC, 4.6L/6AT, 158k, ours
1999 Toyota Camry LE, 2.2L/4AT, 223k, his