Site coverage ratio, permeable paving for outdoor facilities

We are slowly dealing in more detail with the outdoor facilities or the course of the access road.

According to the development plan: floor area ratio = 0.3 and plot ratio = 0.7, additionally there is the following addition in the written part:

In the area of the property's open spaces, only permeable paving, grass grid stones, and the like are to be used.
and that up to a maximum of 20% of the non-buildable plot area?

Am I allowed to normally exceed the 0.3 floor area ratio by up to 50% with ancillary facilities, so 0.3 + 50% = 0.45 floor area ratio?

But now only by 20%, so 0.3 + 20% = 0.36 floor area ratio, or how does it behave with the 20% and the definition "non-buildable plot area"?

Plot is 668 m² (state R.-Pfalz)
House, terrace, carport, and shed are currently planned with 203.11 m², so 203.11 / 668 = 0.3

If I now make 40 m² of driveway (which is tight), then I am at 243.11 / 668 = 0.36 floor area ratio, or how much may I theoretically still pave for the driveway? Or am I allowed up to a floor area ratio of 0.45?

I would interpret it as meaning that 20% of the non-buildable area for you is 669-203.11 = 465.9*0.2 = approximately another 93 m² that you are allowed to cover with permeable paving or something similar. will certainly be able to clarify this in more detail.

Is it always allowed to exceed the floor area ratio for the outdoor area by 50%?

We have a floor area ratio of 0.4 for a 664.² plot... That means how much am I allowed to build over?

Does that require a special permit?

Unless the exact wording of the formulation suggests otherwise and there are no further textual provisions regarding the floor area ratio, the 20% must be considered completely independently of the "normal" floor area ratio.
Assuming your plot is a rectangle of 20m*33m=660m². Parallel to the street boundary line, there is a building boundary at a distance of 5m and another at 20m. Then the buildable area is 15m*20m=300m². The non-buildable area is therefore 360m². You may then build on 360m²*20%=72m² of this area with the facilities permitted by the development plan. In addition to the calculation of the floor area ratio/floor space index, proof is required that your planning complies with this limit.
House and terrace are main facilities that must lie within the buildable area and count towards floor area ratio I (0.3). Carport and shed are ancillary facilities that, unless the development plan explicitly excludes this, may also be located outside the buildable area (is that the case for you?) and count towards floor area ratio II (0.45). Depending on the actual building envelope and placement of your structures, very different sizes of driveway areas can remain.

Is it always allowed to exceed the floor area ratio for the outdoor area by 50%?

Only if the development plan has been made available after 1990 and makes no other provisions.

We have a floor area ratio of 0.4 on a 664m² plot... How much am I allowed to build?

Under the above conditions, 664m²*0.4=265m² with main facilities and 664m²*0.6=398m² in total.

Does that require a special permit?

No.

Thank you very much for your response!

So the development plan was definitely created and made public after 1990.

It is a corner plot which has a 3-meter-wide "construction-free strip" on 3 sides.

House and terrace are within the building window, shed and carport as well, however as boundary construction to the neighbor.

It mainly concerns the intended driveway (which was submitted and actually also approved) that I probably do not want to pave as generously as shown in the plan, but the area will probably be about 80 m².

Or do I not have to worry at all, since the plan was submitted and approved as is? The driveway was indicated and drawn. There was only a note that I had to comply with the middle wall heights for carport and shed due to boundary construction. Otherwise, there were no restrictions as it was an approval-free procedure?