You have done the best test possible. You should now know your AT. Everything should be based off of AT. LTHR and FTP are pure fiction. AT and LT are not the same thing. At is a red line, go over it for to long, 5-7min and blow.
more info on LT.http://www.coachr.org/lactate.htm
You should have received a chart or numbers that give you your Anaerobic threshold, ie the max amount work that can be done by the body with the amount of oxygen you can take in before the body has to take extraordinary means to go harder. HR at AT is fairly constant over time, assuming a consistent active life. My HR at AT has only gone down by 6 beats in the last 15+ years and I am in my late 40s. The amount of work at that HR does change. 30-60 minute output is a performance measure not a physiological measure, nothing magical happens in your body after 30 minutes, muscles just get fatigued.
Try these to for intervals at VO2 maxhttp://www.enhancedfp.com/sport-specifi ... y-thibaulthttp://www.athleticsearch.com/thibaultgraph.pdf
The difficulty with basing training zones off of HR at AT is that the shorter the time frame of the effort, the more it is the ending HR of the interval not the starting HR. With out power you would need to guess your pace such that your HR was at AT after 2 to 3 minutes. Zone2 HR based off of AT is very good.