Hi Dev,
Is it normal to have a ~14% CPU's permanently usage for run the wallet?
Hi, it really depends on what your wallet is doing. If its behind and actively syncing then you could see some CPU usage but if you are all synced and in normal state, CPU usage should be pretty low as you can see in the screenshot below...this is my wallet currently at normal state which is only using 0.5%.

Strange, but I have the same problem ~15% used and the only think I do is stacking...
EDIT: Also I have invested like $15 and for the 3 days I got my first mined coins (calculated I will make $0.27 for full year) is my math off or this is normal with such small amount?