Yes you should uninstall MSE, having two resident scanners installed is one too many and not recommended as rather than provide twice the protection it can cause conflicts that could leave you more vulnerable.
Your problem comes from:
- Detections in Memory - My guess is that you are doing a Custom scan in which you have elected to scan Memory and that all these detections are in memory or are listings of files that can't be scanned. Since they aren't physical files they can't be moved to the chest, deleted, etc. so there is no action that can be taken, hence the Apply button being greyed out.
The detections in memory are frequently other security applications loading unencrypted virus signatures into memory. Having set off a scan of memory by an antivirus application looking for virus signatures, don't be too surprised if it finds some in memory.
So if you can give some examples of the items in the list and the type of scan you did it will help us to help you.
The other ones at the bottom of the list are old avast definitions folders that have been cleaned up by avast doing a bit of housekeeping, so nothing to worry about there.