[Dave Paine]

Many woods are water resistant.

I think the issues is the cracks. Likely denser grain and the finish did not absorb well, or the cracks exposed the end grain. Most woods will absorb more water from end grain vs face grain.

I think you will have a difficult time repairing the finish. It will likely be easier to sand the top down to bare wood and re-finish.

Try to find out the present type of finish from the store where you purchased the table.

 

[Dave Paine]

The crack in the first 4 or 5 photos is where a branch was crossing the trunk, commonly called a knot. The knot will be end grain - and tight grain. I am not surprised it cracked. I see this in the log sections I have for turning.

It will stabilize as the wood approaches the moisture content of your house. If you had standing water from the rain, it may have absorbed some water.

I would not worry about the crack, as long as does not get much bigger, which I would not expect.

Without knowing the present finish, it is difficult to say what other finish, wax or oil can be applied.

You can try mineral oil on the white areas, but it may make these darker if it absorbs.

You can try wiping a small hidden area with a piece of paper towel soaked in denatured alcohol (dna). If the finish does not soften with the dna, you can try wiping the white areas with dewaxed shellac, available in big box stores as Zinsser SealCoat. The solvent is dna, hence the need to test first.

The SealCoat will seal the white area. Not sure what it will do for the colour.