Do you have permission to install? Have you tried to install as Administrator? Is it a school pc? Do you also have another java version installed? How was your vacation?
Technic Launcher works fine, just don't allocate 15 GB for tekkit legends, especially if you don't have all 15 GB available. Use 4 GB max for a modpack like tekkit legends. No, more RAM will not improve performance.
Yes. That's a red message. It is also completely useless.
You've made a Forge 1.14 modpack. Don't bother. Unless Forge changes their installation, it won't work.