You cannot have faith that believes in the justification through the Lamb but rejects the faith that believes in the power and willingness of the Father to recreate us in the image of the Lamb.
To claim that God asks us to do something we cannot possibly do is an insult to His character. Sure, God gave Israel commandments they didn't keep, but not because they couldn't, but because they went about it the wrong way. They went about establishing their own righteousness...trying to obey in their own strength...rather than trusting God to do for them what they could not do in and of themselves. The just shall live by faith. The Israelites in front of Sinai promised God they would obey. God did not ask them to promise anything. Just as He doesn't ask you to promise anything today. But He does ask you to believe. When God says thou shalt not commit adultery, He is not asking you to act, He is asking you to believe! Its a promise more than a commandment. A commandment to the unbelieving, a promise to the believer.
To write off the law altogether and make Moses some sort of despotic pariah just because of your lack of faith in God's power to recreate you in righteousness, is a revelation of such a lack of faith that it could well keep you out of the kingdom. It is a similar lack of faith that kept Israel out of Canaan.