You from Utah?

15 feet is going to be a minimum just for the crabapples and the redbud. If you want more privacy you'll need to remove those. In the very end when all things are considered, i.e. especially pruning, you've already selected the wrong trees. Should you plant any conifers between them and decide pruning is your way to go, I'm thinking two conifers would not maintain any sort of a balance, look...

You need to decide if it's deciduous you want to keep or re-do the job, differently. 8 feet brings more potential problems into the equation as well. You get some jackoff neighbor who decides he doesn't like your trees creeping into his property, he's going to hack them to pieces.

Wrong trees for the place..........

You need to consider a plan with a mixture of fastigiate trees/companion shrubs/and narrow-weeping trees.

Some suggestions for a gardening-look:
Fagus sylvatica 'Black Swan'/'Purple Fountain'
Ginkgo biloba 'Princeton Sentry'
Acer rubrum 'Red Rocket'
Quercus robur 'Fastigata' (var. fastigiata)
Abies alba 'Green Spiral'
Picea omorika: 'Pendula Bruns'/Gotelli Weeping'
Abies concolor 'Conica'
Abies balsamea 'Weeping Larry'
Thuja occidentalis Holmstrup Yellow (deer it's been told to me do not eat many golden plants). It could be myth.
Thuja occidentallis 'Malonyana' 'Malonyana Aurea' 'Degroot's'
Cupressus/Chamaecyparis nootkatenis 'Van den Akker'/'Jubilee'/'Strict Weeping'/'Moonshot'/'Sparkling Arrow'/'Green Arrow'
Picea abies 'Cupressina'
Picea pungens 'Fastigiata'/'Blue Totem'
Picea engelmannii 'Bush's Lace'
Metasequoia 'Sheridan Spire'/'Waasland'
Pinus cembra 'Stricta'

All zone appropriate for your climate (you'll need to look them up or mention where you live).

The Deer, the sharper the foliage the better: spruce for example. You'll need to cage them until the trunks have enough size to handle the deer browing. Probably 5 or more years, each winter.

Add your favorite shrubs into your border mix....spend an extra 1000 dollars, and you are set! ;-)

Dax

A solid hedge of brown leaves might look interesting: i.e. Diablo (Ron's gonna call it something else) Ninebark planted every 3 feet might take care of business. Then you could keep your three trees and have a hedge to annually prune. Ninebark grows like hell too. It's a great hedger. The bark is good winter interst, as well. And if any new neighbor doesn't want your flowering trees on his/her property, prune them in a flat Japanese style so the branches stay within your property line but creat a super-unique appeal. Professional fruit tree pruners could help you get your trees trained in this type of manner when they start to get to a height of 8-10 feet. You could shape them so they extend into your yard 'a bit' too.

Some things to think about . . .
Here's my Idea:
{{gwi:652354}}

Hedges don't need to be straight lines... you can get creative you understand as you continue one each direction from the outer edges of your trees as well. Diablo Ninebark (Physocarpus opulifolius 'Diablo') is extemely drought tolerant with a bonus of white flowers similar to those of lace-cap viburmnum's and are slightly-fragrant. Fall color is decent.

Dax

It's one of the better known shrubs that tolerates shade as well.

See ya,

Dax

Thanks Dax for the advice. I will have to think about what I really want in this space. One semi-related question. I have noticed when I see pix of conifer lover gardens, they plant them close with the plan to cut them down when they grow too big for their spot. Other then the pain of having to cut stuff down is their any downside for putting trees and conifers too close to each other? Just curious.

I simply call it bad spacing or, enjoyment for a certain amount of years. Take your pick.

Dax