What about Baptists like me who celebrate Easter and Christmas - is there a penalty? If I cannot obey the law 100%, is my faith in Yeshua [Yahshua] sufficient for my salvation?

I don't know about you particularly, but most Baptists believe "once saved, always saved"; I believe we are saved when we are resurrected in the first resurrection. Right now, we are saved by hope, as Shaul (Paul) says in Romans chapter 8. And James chapter 2 says that faith without works is dead; so although it's not my place to judge one (in a condemnation sense), I believe our heart should be 100% for keeping Yahweh's commandments and when we fail, Yahshua is our advocate. Beware, our heart must be like David's, not like King Saul's.

If you learn that Christmas has pagan origins, you should have nothing to do with it [Deut 12:31 You must not worship Yahweh your Elohim in their way, because in worshipping their mighty ones, they do all kinds of detestable things Yahweh hates. They even burn their sons and daughters in the fire as sacrifices to their mighty ones. 32 See that you do all I command you; do not add to it or take away from it.].

I think this is rather clear; Yahweh does not want us to determine how we should worship him, but we must worship him as he has directed with his Sabbaths and New Moons and Biblical Festivals at the appointed times of the year. Many say, "but I'm taking these once pagan things and making them good by offering them up to "God"; this statement reveals misguided intentions and ignorance of the above quoted scripture. I am not the one to say whether Yahweh will overlook this, but I would consider why Paul said to work out our salvation with fear and trembling!

May you continue to advance in the knowledge of the truth and uncompromisingly walking in it.