If I take a relativistic frame of reference. If I take an 'absolute' non moving frame of reference, gravity shows up as a force. I use the later for calculating loads and statics, even though it's technically not correct. And in that case gravity shows up as a force.

There are many things than we experience as distinct forces but may not be actually if you change the reference (ex: centrifugal force is inertia) or if you go deeper into unification (ex: electrostatic force and magnetic force can be unified into electromagnetic force). But physics is about modeling reality in a convenient way for you current reference, we will never be certain to have the "real" final model independent from our observation bias.

We don't know. Right now, relativity and QM fundamentally disagree on what gravity is. Both are also hugely accurate in their predictions. QM treats it as a force comparable to EM or the strong force. GR says it's space itself moving. The force we experience is just a reaction to us trying to stay still, as space moves through us.

Beyond that, defining anything as fundamental is a challenge. How are you using fundamental?