I just changed to the same strings per recommendation of the previous owner of my guitar, only the treble side though
. I thought it'd not be surprising, the "Goldin" color of the bass strings is too obvious. I like the sound, very powerful trebles. However, do you have intonation problems with the upper frets? My G string is okay up to the 8th fret. From the 9th fret up it's 10-14 cents sharp. I think I got defective strings
You can read about string crossing, the piece Leccion 5a is mainly for practicing that. I'm sure you will get used to that very quick. Just feel the optimum angle of the strokes for each finger, the hand will follow. Also practice damping with your thumb, it will move up/down along with the hand when you do string crossing.
I think you're on the right path. With more practice your playing should be more fluent. I suggest curving your LH fingers more when you fret down the notes, especially the 3rd finger. Also, in Si Si Re you damp the ringing notes with the RH fingers as indicated in the score, not the left hand.