If you could post a reference track I'd be glad to take a look for you, but I'll just throw something out there anyways.
As for the thing that speeds up as it builds more, first thing that came to my mind was an Arp. I could be totally wrong here, but I know I've personally done this in one of my songs where I sped up an Arp: on Sylenth1 click the 'Arpeg' box and then from there you can modulate the Time and Gate of the arp
Time: How quickly the next note in sequence will hit
Gate: The gate time is sometimes given as a percentage: When it's set to 100 percent, each note in the arpeggio will last until the next note starts. When the gate time is less than 100 percent, there will be a gap between the notes
Be sure to check out the Velocity and Key features as well. Play around, there's a lot to learn! (PS take a masterclass to fully understand your synth. It's invaluable)
