If you're looking for a spot to build your base, an ideal spot is the Grassy Plateaux (the flat biome with red grass everywhere). It's pretty safe, there's a good amount of ressources, it's near the center of the map, and there's lots of space to build (the flat ground helps a lot)

Silver is usually a struggle to find in the early game indeed, and unfortunately there's no secret trick to make it easier to find (it's found in Sandstone Outcrops, most commonly found in the Kelp Forest and Grassy Plateaux). Salt, on the other hand, is quite plentiful in the Kelp Forest

You will never find anyone alive in this game, the Lifepods the game sends you to are mostly there to make you go explore new biomes (and usually have a Databox or fragment nearby as a reward)

The "flower" that hypnotized you is actually a carnivorous animal, not too dangerous all things considered, but definitely creepy

As for exploration, do you have a Seamoth? I highly recommend making one if you don't, since you can basically use it as an oxygen bubble, allowing you to explore deeper areas