To stop the vine weevils, I usually find an old hanky of my husbands (no wonder he is always wanting some for Chmas) and place it at the bottom across the hole. As they are cotton it still allows moisture out, but should stop weevils getting in. I read in Gardeners World mag that to lift them off the ground slightly, as the beetles can't fly or climb. Having said that on emptying a rose I had had in a pot for 3 years, The soil was riddled with the grubs, pure white c shaped maggots with black noses. I was amazed at how many!
Actually, vine weevils can climb very well indeed (even up glass!), but they can't fly, as you say. I've even had them in hanging baskets supported only by wire, so they are pretty good acrobats - the squirrels of the insect world, if you like!
If you don't have old hankies to hand, a J-cloth or similar lining the lower section and base of the pot will help to keep out beasties such as vine weevils and woodlice. Or (possibly, but not tried), any odd scraps of horticultural fleece would do the job,