Is not lifting one's foot from a box containing money inscribed with Quranic verses, knowing that the money is there, considered an act of apostasy or falling into a grave sin? And what are the consequences of not waking up early to send the question?

Placing one's leg on a cabinet does not reach the level of disbelief (kufr) or expel the doer from the fold of Islam, especially if the questioner is suffering from Waswas (obsessive whispering), and he must ignore such whisperings. There is no harm in placing one's leg on a cabinet if there is no intention of disrespect or degradation.