Is the questioner considered sinful for the internal struggle she experiences due to her husband's intermittent prayer and his pretense of regularity, especially after her first experience with a non-observant husband?

One is not permitted to miss Friday prayer except for a valid excuse, and shyness is not an excuse. There is no harm in praying on a chair for the sick. The husband must be warned against neglecting Friday prayer, for Allah the Almighty says: {O you who have believed, when [the adhan] is called for the prayer on the day of Jumu’ah, then proceed to the remembrance of Allah and leave trade. That is better for you, if you only knew.} And the Prophet, peace and blessings be upon him, said: "Indeed, some people must cease neglecting the Friday prayers, or Allah will seal their hearts, and they will then be among the heedless."

The wife must advise her husband with kind words and gentleness, and not expose his shortcomings to others. She should also increase her supplications for his guidance and righteousness, and be patient and enduring.