I think an hour is enough time. It's a small market. I did a quick walk through, then went to the booths that caught my attention. The handmade lopapeysa sweaters.

I checked their website, it looks like that you're in luck. They are open every weekend from 11-17 (11am-5pm). Have a great time!

We were there from 4:15 - 5:00. The food area was cleaning and putting away food starting at about 4:40. We tried to get food last minute, about 4:55 and were too late. Food was gone

I dont remember seeing any there. Its mainly clothes, books, nick nacks etc

Opens at 11 AM

On their FB page in response to a question asking if they are open over Easter weekend - jáþað verður opið skírdag, laugardag og annan í páskum frá kl. 11 - 17. Which roughly translated is 'yes, we are open over the Christian holidays on Saturday and Sunday, 11am to 5pm. Hope that's more helpful

The market is not 'the best' place for sweaters or much of anything. it is an OK market and worth looking in but keep your expectations well under control. If you are travelling outside of Reykjavik you may do much better than in the city. We had the good fortune to buy one for about $150 CAN in Seydisfjordur from a home knitter.

There is a modest food market at the back where you can get a variety of seafood. But this is only when the market is open which is on the weekends.

Not sure about "sand". But there were several vendors selling jewelry made from naturally rounded basalt beach pebbles.

Quite a lot of vendors take card, and for those that do not, an ATM is provided next to the exit so cash is easily accessible.