it gets to be real deceiving trying to figure out what a generator can power. they have a continuous rating and a surge rating. the surge will handle so much load for a very short period of time. it helps with motor load starts. usually when portables are hooked into a house the homeowner turns off the larger 2 pole breakers...a/c,range, water heater.... and they cycle breakers as needed. i have customers that will flip on the well breaker to top off tank, then turn off well and flip water heater to heat water. they cant run both at same time on a small generator. but most houses can use a generator to power up all lights and refer,freezers etc without issue on a 7500 watt generator.
i had one customer that was having an issue with his portable as it kept shutting down randomly from overload. i came out and we determined an extension cord ran out to chicken coup and its heat lamps was the problem. it was just too much to be placed on one leg even though the other legs were way under rated power. in theory it should have worked...but it didnt.
im not sure how your unit can pull 70 amps on one leg at any time, as it only has 2 20 amp circuits on the onboard outlets. but i guess if it was run thru a 240 outlet to the house panel, and all your circuits were being fed by one leg of your houses 2 leg system, but no house is wired that way. i have easily installed 100 manual interlock systems over the years, and i have had maybe 3-4 complaints about overloaded units. those are usually caused by leaving the 2 pole breakers on.
on your generator the 50 amp cord output is protected by the generators main breaker. i have no idea what that breakers rating is.
