Hello Yardbird,
as this is a community forum, where users like you, experiencing all kinds of trouble with their Fairphone, you will find quite a lot of reports like yours if you start some searching.
But don’t just judge on that impression, as the users having no troubles are comparatively rare guests here.
As this is a very competent community with lots of techies and developers, you usually will get some help within a day.
The battery is a known weekness of the FP2, although it should not be as extreme as you report. To start with, you could take a look at the batteryguide (follow the link 
).
When the phone gets hot (above the battery, right?), this might be due to an app or a background process “running wild”. That at least was the case for me. I simply turn the phone off and start it again (sometimes twice or at worst three times) and the heating problem is gone.
An app known to cause more trouble than any other seems to be the original Facebook-app. If you should use this one, try to switch to another app.
I have no idea or recommendation, as I don’t engage on social networks.
The microphone is another week spot in some phones, that normally is solved by exchanging the bottom module under warranty. For that you have to do the troubleshooting-tool and if it doesn’t help contactsupport (send them a mail first and then call with the necessary numbers at hand: order-no, IMEI and ticket-no.).
I fully understand your frustration, but I don’t think your experience is exemplary and you really should give it a chance.
If you are on tour quite a lot, maybe a small powerbank might be a solution? I know, that’s not how it’s meant to be, but it’s a possibilty.