ok, had a little mess about. i think your best bet for the sweeping sound, is to just use the flanger, so you can just bypass it when needed. i got pretty close using the stereo jet type, rate slow, depth maximum, feedback -97, through zero on, phase 0deg, mix 100%. i put it after the cab. now i know the sweep on the original starts low and ramps up to some high value and stays there, but this isn't possible unfortunately...even using the adsr...but i don't think it will matter to be honest with you. there also seems to be another sweeping note on top of the chord, but again...it's the general sound you're after...the audience won't notice the difference.
as for the chopped part..it sounds like the flanged tone, but with a tempo synced gate on it. you could simply do this with the tremolo set to square, but it will be hard to use this live, because you can't control when the cycle starts. a better solution would be to use a volume block, with the level tied to lfo1 set to square. you must then tie the run parameter to envelope and bump up the mid level of the curve. this will then start the lfo running when you hit a chord.
you could get closer using the synth block, but just for ease of use, sometimes it's better to go simple. you can add the flanger and volume block to the rhythm patch you're already using for this song. if axe edit was up, i'd probably have a crack, but it's such a pain trying to do it from the front panel (for me)...
