I tried BleachBit (from the deb depos), and while it worked fairly well (I recovered at least a few gigs of disk space), I'm facing a new problem. The default terminal setting had been removed. There are at least two instances where I need terminal access because calling it from the Menu or the Run option won't work. [NOTE] If it makes a difference, I didn't run BleachBit as root.
[1] Calling a terminal from inside a folder - sometimes this is necessary because shell scripts seem to have problems navigating between directories. After running BleachBit, I got the message 'terminal emulator has not been set'. I tried selecting LXTerminal, but now I keep getting the message on the Subject heading of this post.
[2] Clicking a script brings up a dialog that asks whether or not I want to run the script in a terminal. While I would like to change this (because some programs won't run if I select the terminal option), it's still worthwhile because some apps like DOSBox will give useful info in the terminal if the app fails to run. Since I can't figure out how to change the default terminal, I can't do any DB troubleshooting.
Also, I just did a system update, but all it updated was the Wine install and possibly some of the multiarch code.

Debian 8 Jessie 64bit

Probably bleached out user initialization files, you can copy a new set over to your home from /etc/skel.

you know linux is case sensitive, right?

so,

also try "lxterm".

I tried copying the files as suggested: no change. Into the Home folder had no effect, so I looked in my $NAME folder (as in /Home/NAME) and I saw duplicates of the same files. So I put them there, but no change even after reboot.

Since you didn't run it as root there cannot be any damage to the system, the problem must be in your home directory. Have you tried creating a test user?

I found a tip on the aboutdebian page that suggested editing the bashrc file.

export TERM='LXTerminal' *or* 'xterm*

Then to activate it without having to reboot:

echo $TERM

But for some reason it always returns 'xterm'. Maybe it's because that's what I set it to the last time I tried it, in the 'Open with' option under File Properties. And just to further clarify, the terminals (any of them) run just fine when called from the Start Menu (or whatever Debian calls it). But if I need to run a terminal-necessary command inside a folder, or if an app needs to 'Execute in Terminal' in order to function, it fails because it wants 'LXTerminal', which is claimed not to exist.

On Emerson's first suggestion: to clarify, the three files from /etc/skel were already in my home folder. Since editing/overwriting the home files had no effect (not removing the /etc/skel versions - only edited the terminal setting), I'm inclined to think there's another setting somewhere affecting this. Also, since said files were already in the home folder, bleachbit didn't affect them but removed something else. I'd like to know where this mystery Linux config file is - I've lost count of how many times I've edited fstab on Slitaz and rebooted, only to not just see the behavior unchanged, but the changes I made were still present in the file. Some of the previous times I installed Debian 8 Jessie I edited 'system config files' to try to get sound working, but that failed too.
Second suggestion: the second profile is clean. I'm inclined to keep it for test purposes.
Interestingly enough, the default terminal was already set - 'xterm', same as my original profile.