How do you plan to protect the front door? How will you differentiate between a thief and the mailman?
IR beams are still in use though they are one of the oldest and easiest to defeat technologies. If you really want to detect movement across the lawn use seismic detectors. You can also use medium range microwave "beams" which consist of a transmitter and separate receiver. These are far more difficult to defeat / bypass than IR. I sell them to prisons every so often.
If you want to sleep with open windows consider using wired alarm screens. When wired properly these are difficult to defeat and they're far less costly than what you propose. They can also be installed with far less damage to your trim.
Leaves and other gunk accumulating in gutters will inevitably cvause false alarms. If you want to detect a roof intrusion, use impact detectors on the underside of the roof.
Uh, no. That is not correct. In 24 years running an alarm company I have dealt with exactly three cases where thieves tried to penetrate the roof. In two such cases the alarm signaled the police whiule they were inside. The other didn't have an alarm. I sold them one after the robbery.
Who is going to man your base?