3.5 amps would be the max continuous amps, aggregate for the transformer. I don't know where you got the 155 or 0.4 figures. 115 volts is the input from the wall receptacle; it is not something generated by the transformer.
FYI, the 75% continuous rating was given by Lionel itself in its Model Railroading paperback back in the 50's/60s. Also, the breakers in those old postwar transformers were not particularly good. I will leave it to others to comment of the maximum continuous rating for modern transformers.
A handy gadget to have is a cheap AC ammeter. You can ascertain the draw of each device.
Googling, I dug out the section of the Greenberg repair manual covering the 1032, including the schematic. Quite frankly, I can't figure out which combination of terminals are protected by the internal breaker. I'd fuse or breaker all leads
The manual does say the internal breaker when new would open in 7-8 seconds on a dead A-C short, but aging will increase that duration. No mention of protection for other post combinations, such as A-B, B-C, etc. The manual does say that not more than 50 watts should be drawn continuously. This would equate to 0.67 rather than the 0.75 figure I used. But it also says to limit continuous amperage to 4-4.5 amps. If you have much older Lionel equipment, the Greenberg Repair & Operating Manual for Lionel Trains is a worthwhile investment.
Having said all this, in my younger days, back around 1950, I use a Type R (100 watts) to run two locos (#224 & #736), 2 022 switches, and a #97 coal elevator.
