I also think one of your md5_sums_***.php files is broken because the results aren't useful. One of your addons is interfering. Their corresponding md5_sums file will be loaded even in they are disabled.
The problem with converting to vBulletin 5.X is that you will need to convert the database to UTF-8, which vBulletin 4.X doesn't support. We have scripts for this purpose now so you can convert the database after upgrading. It isn't something that should be undertaken lightly. You can't have the random files everywhere with vBulletin 5 as you do in vBulletin 4. It can lead to errors. For your site, upgrading will be a major undertaking.
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