Joe,

Amidon and the other toroid core manufacturers should have data sheets for their products which list power saturation curves as a function of frequency. From this it should be easy to determine transformer heating for a given frequency, winding construction and applied power level. There should also be a "do not exceed" value noted as well.

As far as ladder line spacing goes, I'd use EzNEC or a similar antenna modeling program. There may be an online version that you can use.