One more bottleneck item: clay sculpting tool for pottery - never found one in 3 starts .. especially not with 3+ months start or rare item spawns

Tongs don't really need a replacement, you can make one-use tongs from wood easily. Besides, the new spawns place them in houses with fireplaces very often.
I'd suggest Knapping Tools, for example being able to dismantle deer head trophy to get a deer skull. They have been taunting us for a while...
Maybe cross-use of metalworking chisels for masonry?

I would really like to stumble on a Mod that clears up all the bottleneck items for playthroughs involving jumping straight into the wilderness. The hacksaw, rags, nails, and quite a few other things don't allow playthroughs that let you survive if you were to spawn deep in the woods. When Ysaaro fixes his Spawn Anywhere mod to be able to spawn in the woods I'd like to at least have the chance to survive if I'm stuck but also going on no loot runs would be fun as well. The game is too easy for me so I'm always looking for a challenge.

You can craft small iron bands from iron bands which can also be forged now.

My suggestion for another bottleneck item is "small iron band" - unless that has been added in a recent update it is impossible to craft despite just being a bent piece of metal, and blocks access to the wooden bucket needed for an advanced forge.