We went through MAD last weekend on the way to SVQ, so the dynamic is the same. 55 minutes would have been easy, even if not spacious on time. The train from T4S->T4 (including escalators/elevators and such) will likely be the longest part of the journey. Immigration was very quick.

With the longer connection, you'll have access to Sala Dali, as mentioned. Medium-level lounge in terms of offerings.

On the way back, go straight to T4S and the Sala Velazquez. Much better.

Cheers.