I cannot guarantee until I go look at my car next week, but I think if you remove the scoop, then the upper grommet for the washer hose in the second of three photos, you can probably see the lower grommet in the front of the heater chamber, through the upper hole. According to the placement of the water inlet and outlet holes in the firewall, the heater core is lower and farther inboard. I suspect that you could remove the two grommets, insert a coathanger wire through the upper hole, then straight through the lower hole, clamp the wire around the end of the hose and pull it through the chamber and both holes without being concerned about the heater core, which is farther to the right and lower. The grommets can then be installed from the two exposed ends of the hose. Finally fish it through the firewall hole at the lower end and attach it to the spray nozzle at the upper end. Reinstall the scoop and you are done. It might be even easier if you disconnect the pivots of the flapper door of the scoop.
Anyway, don't give up. Good luck.
Tom Kizer