"2. remove Avast through Programs and Features
3. reboot in safe mode
4. avastclear in this safe mode"
3 should be reboot.
4 should be run avastclear in regular mode, choose which version it is to remove and then allow it to boot into safemode to do it's job.
5 Once done, it will give you the option to boot back into regular mode.
At that time, you should be able to do a clean install. Use the custom install so you can uncheck anything you don't want.
A video to guide you through all these step is available at:
https://forum.avast.com/index.php?topic=93544.msg1201631#msg1201631
I have no idea if making these changes in the procedure make a difference.
I can tell you that this is what worked for me - and, is still working for me. 
Sorry, still not solved.
I followed your sequence and everything happened as you said.
But no success.
Again it happened that Avast said after the clean install there were no updates after 150323-0.
That is also a download problem in Avast itself.
See the attachment (with name "no update available after clean install 2215.jpg") in one of my previous entries.
Immediately after disabling Avast the automatic update to 150419-1 was done.
Tomorrow I will submit a support ticket via https://support.avast.com/Tickets/Submit
Actually, I think you can also consider checking for unusual files and/or abnormal settings on your system.
Whilst we're not saying you've got malware of any kind on your system, something is not right (see above) and it won't hurt to have a certified malware expert have a look-see via logs you submit, while you are waiting for a reply to your support ticket.
To do that, go here:
https://forum.avast.com/index.php?topic=53253.0Start a 'New Topic' (you must be logged on to avast! forums to see this link) and run the first three programs and
attach the logs resulting from running them. Someone will assist you once you start your topic and attach.
There is nothing more exasperating than having a system running the way yours seems to be, and would at least want to have the peace of mind to know whether it is clean or not. Besides, help here is free for all who ask.
Best possible outcome would be to have your issue with avast fixed and the fix(es) only will be specific and personlised just for your system.
