Anaerobic Thresholds

I had my run VO2 max tested a few weeks ago and my Anaerobic Threshold tested out at 160 bpm, which felt about right to me (RPE) and is consistent with the data that I capture in my training logs. Based on all of the other data, I feel like I can pretty confidently construct my training zones for the run (i.e. Z2 (137-145)). I'm a little lost on my bike thresholds. I pulled a few training logs from last summer, I averaged around 130 bpms and had maxes in the 160 bpm range -- these were long (70 mile) moderately intense training rides. I also pulled data from a 70.3 that I did in Sept where I averaged 138 bpm and maxed at 165 bpm -- I probably went too hard on this race during the bike as my run time was 23% slower that my best stand-alone 13.1 time. The other piece of info is that I have a really difficult time getting my heart rate up to those levels on my trainer even though I'm working by butt off. I did an FTP test (i.e. warm up for 30 mins and 20 mins all out) this morning on the trainer where I was going all out. Trainer Road estimated my LTHR at 125 bpm, which seems really low to me although my heart rate was 130-140 bpm during the 20 minute test. My gut tells me that my LHTR outside is probably around 140 bpms. Any advice would be helpful. I'm at the beginning stages of training for an Ironman distance race.