RE: Taking Profits - A Problem Most People Would Love to Have

What is the best way to trade DEC/SPS to Hive?

There are no direct trading pairs for DEC/SPS to Hive, that I am aware of.
On hive-engine, you can trade DEC/SPS for SWAP.Hive
Best frontend for that is probably tribaldex.
Then you need to 'convert' swap.hive to hive

What is the best way to move Hive out of Splinterlands?

That's an easy answer, once you got swap.hive:
https://beeswap.dcity.io/convert

Do I sell assets and take the earnings out?

I would recommend that.
Maybe wait for a good price, first, but what a 'good price' is, I don't know...

Which assets do I sell?

I think it could be a good idea to sell your Splinterlands assets now, or soon.
I think, the ideal moment would have been a long time ago, probably before CHAOS packs release.

Which token do I swap to?

That is the million dollar question, isn't it?
I made a prediction exactly 1 year ago:

https://peakd.com/price/@felixxx/hive-price-prediction

So far I have made 3 predictions, 2 came true, the third is still hanging there and it looks like, I was right again.

What to actually buy or sell and when, is your decision.
The above are my 2 cents and only because you asked.
I think HBD is a safe haven and BTC feels like a pretty safe bet in the long run.

If BTC does not break down entirely, eventually it will be become more and more valuable - the remaining question would be: when.

If you want to move out of crypto entirely, I could tell you where I would invest, but that also depends on how much you got and your character.