This is a game, not a simulator. (besides it simulating things, that's just aside)
If it were 1:1 we would need 10 minutes to get anything into orbit, which is very tedious for most people. I include myself into this category because I don't want to waste to much time on this.
The Delta V requirements in 1:1 are also much greater. It requires very complex staging to do things efficiently and to get the same things done in the regular KSP.
KSP has to be dumbed down so everyone with some faint interest in spaceflight can play it, not just the physicist and the aero engineer.
Most people on here are, but not everyone is.
If your into realism you can download RSS/RO.
I have always been able to fiddle with the manoeuvre nodes from kerbin orbit to get any encounter. Maybe your mouse sensitivity is off or you don't have cool hands to fine adjust using the maneuver icons? If your really unable to get a encounter from kerbin easily you can use the precise node mod...
This will let you fine adjust maneuver node parameters by 2 decimals places.
I'm also not qualified to tell you much about the mathematics concerning oberth transfers. If you haven't looked it up yet, it basically tells you that burning as close to the periapsis is more efficient then burning anywhere higher then your pe. Doing your encounter burn outside Kerbins SOI will thus lose some Delta-V efficiency. In kerbins case this means that doing your transfer burn as close to 70km is the most efficient escape burn.
Also know that getting anywhere close that is from 1-10 million meters from your target (i.e. Eve) is a very close encounter. Doing a correction burn outside the Kerbins SOI usually involves 1-5 m/s Delta-V. So it's not paramount to actually hit the target absolutely close, as long as you have a encounter the correction burn is more then forgivable.
Also note that if you've set a maneuver node in map mode you can use the "tab" key on your keyboard to switch between planets. If your target is Eve you can switch to Eve, pan your camera to Kerbin where the maneuver node is, then fine adjust and keep a close look at Eve and eyeball your vessels orbit line as your adjust the nodes. Using Precise node at this point is very recommended if your aiming for a atmospheric entry from Kerbin orbit. It's hard to get this exactly right in any case, so you'll usually need a correction burn later on.