Actually, "they are as strong as we" is not correct. The pronoun needed here is the object of the sentence, and the objective version of first person plural is "us". "We are" is correct because it is a phrase that acts as the object of the sentence. In this case, We is the subject of the phrase. I am sure that is rather confusing, we native English speakers are known to use the wrong case in certain situations.
Completely incorrect. Here is a web site that helps explain why 'us' is incorrect in this sentence.
Forte is not quite the same as most adjectives, which have 4 different forms (because they distinguish between masculine and feminine). Forte does not change with regard to gender, so it only has two forms: one for single one for plural. That might be the source of confusion here. Here's a good site that explains it
Yes, you are correct, it only has two forms, forte (singular) and forti (plural). I was trying to convey a reminder that adjectives can change according to whether the subject is masc/fem...sing/plural. Even though I know better, I will still make the mistake. Thank you for the clarification. It is worth the additional reminder.