(Portugal, Spain, and Italy) When should I seriously start booking stuff?

Got married recently and we are planning on doing a 30-day honeymoon to Spain and Italy mid June & mid July 2025. I already started looking at flights but seeing they are:

A. Pretty expensive for the US-Europe trips B. Not a lot of direct flights for the intra-EU trips.

We are planning on doing the following:

Spain (start in Galicia – spouse has family there) Italy (end in Avellino – I have family there).

I want to also visit cities in between. ChatGPT recommended filling the void by doing the following, but I am not committed to any of the cities:

Portugal: 0. Porto (just to fly close to Galicia, no direct flights into Galicia from my home airport). Planning on renting a car from there to drive to Galicia)

Spain: 1. Galicia (fly to San Sebastian if possible to find a direct flight) 2. San Sebastian (direct flight to Barcelona if possible) 3. Barcelona (direct flight to Florence if possible)

Italy: 4. Florence (direct flight to Napoli if possible, considered swapping for Milan, have not been to either city) 5. Napoli (rent a car to Avellino) 6. Avellino 7. Rome (just to return rental and fly back to US, no direct flights from Napoli to my home airport).

Does anyone have a better way of doing this trip and insight on if there actually are direct flights for all of the cities above?