Hi, Paco.
Technically, all your three examples are correct. But I think the word 'thrice' is no longer in use in modern English.
Regarding your last question, you can simply say 'four times(300x4=1200).'
If the bridge is 901 meters or longer but shorter than 1200 meters, you can say 'more than three times longer,' not 'three times longer.'
Does this help, Paco?