I think you have too much packed into your trip for such a short time. You lose time every time you move to a new location. You have to pack, check out, drive, possibly get lost, cities are difficult to drive into and out of, check in to your next hotel, unpack or sort of unpack.
Three nights is very little time in Madrid and Seville, and yet you want to do daytrips from each place. Don't forget that 3 nights gives you 2 full days. At the most you will have 2.5 days in those cities. So you only have 1.5 days to see those cities if you go ahead with your daytrips.
How many people on this trip? Don't forget it takes more time to move more people. Unless everyone is very regimented like being in the army.
If it were my trip, and it isn't, I would visit only one country. I love Madrid, Toledo, and Andalucia. A possible itinerary could be Madrid (4 nights) with a daytrip to Toledo, Seville (4 nights) with a daytrip to Cordoba. A night or two in Cordoba would be better. And at least 2 nights in Granada to see the amazing Alhambra.
Or you could spend all of your time in Portugal to include Lisbon, Porto, and a beach area. Possibly with an overnight or two in Sintra.
What month is your trip? The summer months will be very hot. Be prepared with sun hats, sunscreen, and lots of water. Get hotels with pools.
And, yes, Sintra is in Portugal, not Spain.
Good luck!