First off, and I know you said sparingly, but be careful with the starting fluid. You can inadvertantly do major damage without trying too hard. I generally use carb cleaner or Brakleen, still flammable, not quite as volatile. And still just a little, ether was made for old school Detroit diesels and Catapillars that didn't have glow plugs and turned over slow in cold environments. You can blow the tips off your glow plugs and screw up your cylinders real easy.
Charge up your batteries thoroughly, dis-connected, go read my post titled A Word of Caution for some pointers. Scroll down, you'll find it. If you didn't have the starting problem before you changed the ICP sensor, swap it out for the old one, try again and see if that changes it. It's always possible to have gotten a faulty part. If no change, closely ck the connections in the wiring you swapped, make sure everything is good and clean and secure. Gently unplug and re-install the other sensor connectors, it's possible that you accidentally loosened or bumped one and interrupted the connection. Focus on what you changed with this in mind "Did it do this before I changed that?" Don't go off on bunny trails or freak out just yet.