Building along the shore is one of the biggest traps in the game. It takes a lot of work to pull off properly and even then to stop trolls you would need to set up a no spawn zone enough around the area to prevent any spawns from sight aggro.

Safest is to build on top of a hill top and terrace the sides then outside of that dig a ditch/ things can't climb.

It isn't too hard to have a 100% safe base especially at your level.

The game does scale for difficulty depending on player count. I feel solo is well balanced if you plan ahead. Bosses you summon when you are ready... so prepare the area first.

First time through you will die a lot learning the game mechanics. Once you do though it isn't difficult at all as long as you are careful. I do nothing but no death runs now.. if I die I start a new world and new character. So I tend to be overly cautious.. but it certainly is doable for an old man like me.