Richard is a guy who tries to do the right thing. He really does! But the man just can't help himself.
Let's jump right into questions of freedom. Richard has addictions, sex and drugs being the big two. (Well, OK, you could make the argument that music is a third, but there's no way you're going to get us to write "sex, drugs, and rock & roll.") Yet, at the same time, he exercises utter self-control around alcohol, knowing there's a history of alcoholism in his family. This man has principles, but he sure also has desires. And that's a combustible combination.
Richard is also a lone wolf, a solo operator. He is unable to enter into an intimate relationship with a woman, for fear that she'll make demands on his independence. (His friendship with Walter, on the other hand, conveniently requires little of him.) This is what troubles him so much about his love affair with Patty, as he both loses the handle on his cherished self-control and allows himself to become enmeshed in a complicated emotional struggle.
Speaking of struggles: after twenty years of struggling as a mostly-ignored musician, Richard unexpectedly stumbles into mainstream success. And this brings his principles (disgust of the mainstream) into violent opposition with his desires. So he responds by restricting himself as completely as he can: spending money as quickly as it comes in, in order to ensure he remains flat broke. So when the money finally stops coming in, he goes back to manual labor, as a way of paying a penance and reestablishing his principles of all those prior decades.
But what happens next? If we can attribute his affair with Patty to having succumbed to his desires, then what do we make of his conscious decision to destroy Patty and Walter's marriage? Well, one big change in Richard's life after his success is that suddenly he's recognized everywhere he goes. He can't take a subway ride without someone asking for an autograph or whatever. He has lost his anonymity, and, in other words, his freedom – and there's nothing he can do about it.
So, back to Patty: Richard finds himself in bondage, still trapped by his feelings for her and his guilt for betraying Walter. Again, he finds himself robbed of his precious freedom. This time, there's something he can do about it, though. He decides the only way to regain it is to detonate the whole complicated mess. He is, finally, prepared to sacrifice his principles, and destroy the marriage of the two people he cares about most, to be free. Miserable, sure, but free.