Try these then: 1. Tip: Purge the Downloads Queue!

2. (a) Go to LW's menu bar, Tools -> Options -> Speed & disable ultra-peer capabilities, (b) Tools -> Options -> iTunes & disable sharing in iTunes.

Set both uploads & downloads to auto-clear, Close all LW windows you don't need open at that time.
If you're not in front of your comp, then hide LW in the dock/tray.

Don't use the Resume/Find Sources button on all incomplete files. This can have side-fx such as affect LW's connection quality. May queue your files for much much longer. This will also stress LW & your comp. If you use Resume/Find sources then just apply it to a couple or so at one time.