Was Crocodile stronger at Marineford? Or was he holding back in Alabasta?

 During the Alabasta arc, Crocodile displayed a level of power that was initially considered overwhelming by the Straw Hat Pirates. He possessed the Logia-type Devil Fruit called the Suna Suna no Mi (Sand-Sand Fruit), which granted him the ability to control and transform into sand. He had a reputation as a Shichibukai and controlled the desert kingdom of Alabasta from the shadows. His strength was showcased through his battles with Luffy and others. At Marineford, Crocodile was present as part of the war that took place at Marine Headquarters. While he did participate in the battle, he didn't display the same level of dominance as some other powerful characters present. This has led fans to speculate that he might not have been as strong as initially portrayed in Alabasta. It's important to note that power scaling and character abilities can be subject to interpretation and development by the author. Oda often keeps details deliberately open-ended to keep the story intriguing.

In 63 BC, did Pompey see the Ark of the Covenant, or was it empty?

There is no historical evidence to suggest that Pompey, a Roman general and statesman who lived in the 1st century BC, saw the Ark of the Covenant or that the Ark was present at the time. The Ark of the Covenant is a biblical artifact that is described in the Hebrew Bible as being a gold-covered wooden chest that contained the tablets of the Ten Commandments. It is said to have been built by the Israelites under the direction of Moses, and it played a central role in the worship of God in ancient Israel. According to the Hebrew Bible, the Ark was kept in the Tabernacle and later in the Temple in Jerusalem, but there are no records of it being seen or mentioned after the destruction of the Temple in the year 70 AD. Some stories and legends have suggested that the Ark might have been hidden or lost, but there is no reliable evidence to support these claims.