Are Willy's self destructive actions caused by an attempt to act ethically?

To some extent, yes, but to a much larger extent, no. For example, Willy tries to act as a good father to his children, but ends up pushing them in the wrong direction. He encourages stealing but makes excuses for it, "Oh, nerves of iron, that Biff!". He also encourages popularity rather than intelligence saying "the man who makes an appearance... is the man who gets ahead". I don't think that Willy is purposefully bringing up his children the wrong way, I think that he is bringing them up with emphasis on the character traits that he deems to be most important, such as "nerves" and being "well liked". As a result of Willy trying to be a good father, he is in fact bringing his children up wrongly.

After this, pretty much none of his actions are caused by an attempt to act ethically. For example, Willy doesn't make use of the skills he has. He is a very practical man, shown when Charlie is impressed with the ceiling Willy puts up, "Yeah, that's a piece of work", but thinks it is normal for a man to be so good with tools, "a man who can't handle tools is not a man". If Willy wanted, he could use his skills to get another job, more suited to the things he is good at, but his warped idea of what a man should be like means he does not.

Another example is how he cheats on his wife with "the Women". This action is caused in no way by an attempt to act ethically. It is caused by the fact that Willy has a very low self-esteem, and "the Women" 's attraction to him makes him feel better about himself, shown by the repetition of "you picked me?". This shows that action is completely selfish. The guilt from being unfaithful eats away at Willy's conciousness and causes great amounts of guilt, probably resulting in him feeling worse than he did before the affair.