Yes - the RODI should be able to push the DI water up about 9 feet. Due to the head pressure your membrane will perform like it has about 60 psi rather than 65 psi - so you should be OK.
But you have a couple of other issues I'd be more concerned with:
1. We recommend against running your RODI to a float valve in your sump. When (not if) that float valve fails, or is kept from closing entirely by mineral build up, algae, a snail, etc, the RODI will pump 0 TDS water into your sump, and pump, and pump, and pump. If for whatever reason you don't catch this, you'll significantly change the salinity in your tank and overflow the sump. Bad news all around.
2. TDS Creep is a phenomenon common to all RO systems - it results in a pulse of not-so-clean water coming out of the system during the first 60 to 90 seconds after the system kicks on. Here's some data from two different tests that demonstrate TDS creep.
Every time your sump water level drops just a small fraction of an inch, the float will call for water and the RODI system will kick on for a short period of time. And then it will turn off. And on, and off, and on... all day long. We call this "short-cycling." When you allow a system to short cycle, a high percentage of the produced water has a TDS reading significantly higher than 0 ppm. So you end up burning through your DI resin faster than you should, and you deliver low quality water to your sump.
Russ