Unfortunately, blue spruce are extremely susceptible to Rhizophaera needle cast. Most recommendations include beginning to treat when the new needles are expanding about halfway and then following up with a second treatment 3 to 4 weeks later.

Here are some links with additional info and management recommendations:

Blue spruce needle cast disease - MSU Extension 

Rhizosphaera needle cast | UMN Extension 

Rhizosphaera Needle Cast – Wisconsin Horticulture 

Regarding dilutions amount: In looking up that particular product, I noticed that multiple people had noted in reviews that the directions are confusing. Perhaps select a different brand that has clearer instructions to follow for treatment next spring.

Regarding system applications: For certain pests, there are some insecticides that are injected into the soil and absorbed by the roots (and even some injected into the trunk) to help prevent damage. However, needle cast is a fungal disease and cannot be treated systemically.

As far as spraying higher: There are arboriculture companies that have higher pressure large sprayers to treat trees with fungicides. Here is a link to finding an arborist in your area.

Resources - ISA Michigan (asm-isa.org)