Aging in Whiskey Barrel

My friend let me borrow his Charred Oak Barrel while he is attending master brewing school in Berlin. I seasoned it with 1 litre of Woodford Reserve. I swished it around three times a day for a month while my FBS Clone Fermented (very nice by the way OG1.094-FG1.022). I emptied the Barrel this morning and Transferred my FBS Clone into it. My question is: Should I have done something else before transfer? I assume it was sanitized by the Bourbon. Any ideas or thoughts would be helpful. Also, I only ended up with 4.5 Gal in a 5 Gal barrel. Topped with CO2, will the dead space be an issue?

no need to add anything else, and if you put co2 in it no need to worry about the head space.

The bourbon will have sanitized for you, I usually use oak chips and sanitize with bourbon (about 1 cup) but i leave it in there to add a little extra flavor.

I know most people keep them topped off completely so the wood doesn't dry out. I don't know how long you're aging...it might be a non-issue. If need be, perhaps wet towels on the outside? I'm just brainstorming...