On the parallel runway point:
The ICAO guidance is that simultaneous parallel departures are considered to be separated when the runways are 760m or more apart and the aircraft diverge by 15 degrees or more immediately after take off. This would apply in non-visual conditions and relies on radar being available.
In visual conditions, provided traffic information is passed to each aircraft, then no divergence is necessary that close.
760m is generally the limit in terms of proximity, as wake vortex separation must be applied if the runways are closer. Having said that, in the USA there are various ways that ATC can relax the wake separation requirement that are not available in the UK.