I've got two logfiles that are huge in /var/logs/ 250mb and counting...

In the Everything log I have the following repeating every few seconds...

alarm kernel: [61472.910057] EXT2-fs (sda1): error: ext2_lookup: deleted inode referenced: 74575
alarm syslog-ng[1217]: Error suspend timeout has elapsed, attempting to write again; fd='8'

And in Kernel

alarm kernel: [61472.910057] EXT2-fs (sda1): error: ext2_lookup: deleted inode referenced: 74575

Any idea's how to fix these errors? My usb stick fills up in about a day with these!

You could try a fsck to start with ... I'm not aware of any particular caveats with flash drives.

Is there a particular command I should run after it? like -a etc? I know there are a few variants that do different things. But I don't
really understand the differences

You don't want to run it on a mounted file system so try booting to single user or depending on how you've laid it out you might need to boot off a livecd. Try 'fsck /dev/sda1' first, then if it complains do as it suggests.