Gaussian calculation problem - Maxcycle values for Opt and SCF
You are mixing two independent, but slightly related topics.

First is the SCF convergence, i.e. obtaining the wavefunction. This step is necessary for any calculation, without it the Gaussian crashes. For well behaved molecules, as the prostaglandines (organics) most probably are, the solution should be found fast (&lt;30 SCF cycles). It also does not matter which converger you choose, i.e. QC or DIIS. How "tight" you decide for the SCF affects the final energy, but only the number of digits (precision). The SCF does not have any "verytight" option, according to manual, only the Conver=N.

On the other hand, the integral and grid settings do have effect on the energies, so all calculations have to be done with the same grid. I won't recommend changing the acc2e settings, the error is negligible.

Regarding the geometry convergence, you should obtain an optimized geometry in less than 100 steps for reasonable organic systems. If this does not happen, something is rotten in your setup and you should look deeper into the problem. In principle, you cannot converge the geometry to "tight" without sufficient accuracy of the SCF, namely the ultrafine grid, which you now do use.

How good the optimization was can be guessed by the frequencies which should be zero (translations and rotations). If they are significantly off, optimize the geometry more tightly. But as said above, you cannot optimize on noisy surface, where the noise is produced by the grid and SCF convergence.