I see you haven't been officially welcomed. Since registrations have been closed for a few years that means you've been lurking.
Consider this an official 'Welcome to the Forum'
Al

On your issues. The 100# filter is WAY too small for that sized pump. I'm not getting detailed but a 1 HP can be sized with a 300# filter nicely. You can never go wrong with an oversized filter. The larger the filter, the slower the flow through the sand bed, lower pressure, and better filtering. A couple years ago I dealt with this place in Florida on line for a Hayward pump.
http://www.inyopools.com/
Prices and delivery were very good. There are bunches of other places too. Also, there is no advantage to buying units as a pair. Filters are filters and pumps are pumps and they all hook together basically the same way.
Others will kick in with their comments.
Al