Sorry to hear that it didn't work well for you. I'd like to help clarify some limitations to the importer/HLO exporting/FoundryVTT PF2e system. Some of these points may come across as "excuses", but hopefully it helps.
Equipment: The importer works by attempting to locate the best match for each item from the PF2e Compendiums and adding it to the actor in Foundry. This helps to keep the importer simple and avoid breaking things by trying to be fancy and create an entire actor from scratch. In the case of inventory items, it does not handle runes/materials at all. This is because the exported JSON from HLO will simply state that you have a "+2 Greater Striking Flaming Silver Longsword", and then I would have to parse every item, figure out if it may have runes/materials, and then find the underlying item (longsword in this case) add to actor, then add each rune/material separately and hope I didn't break anything in the process. For myself, partly because HLO API does not currently have a system to import characters, I only intended to have the inventory attempt to import once, for a new character, rather than try to maintain equipment on both platforms simultaneously. All that being said, I'm not sure if that was your issue, but it is likely that, or your added custom items, or something weird happened with how HLO and Foundry label their respective items. For Armor, again, the importer does nothing to set values on the actor, it only adds the item and lets the system work its magic. This is probably a case of having runes on the armor.
Languages/Attributes: Attributes are only in respect to your str, dex, etc. and do not affect languages. For languages, that should have worked, though there may be issues if you have selected extra languages that you normally shouldn't have received, though I would be interested to know what your circumstances were and what results you got. (i.e. were you importing over an existing actor in Foundry or a fresh one. Did you have feats/others that granted additional languages.)
HP: This is a strange one as per the PF2e rules, you only get a set amount per level based on class/ancestry with Toughness being the rare exception. Not sure what you had going on that would allow for a different HP value. Feats being added 'should' auto-magically increase HP based on the rules in the PF2e system in Foundry, but any errors there are beyond an issue with the importer. (You can't even manually set max HP value in Foundry)
Feats: These are a hot mess, and here is why. HLO does not provide much, if any, metadata with the feats/spells/et al. So it is up to the importer to 'guess' where they are supposed to be, and at what level you selected them. If it can't figure that out, it goes to "Bonus". Nothing I can really do about that. It does it's best to account for double feats, but some feats are allowed multiple times, and Foundry PF2e system will auto-add some feats when they are granted from another feat. I wish I was able to handle this better, but I won't be able to unless HLO gives some more data, this is all I can do. (I have contacted them regarding this and because the HLO systems does not track levels of feats, that won't happen. But at least knowing the category would help tremendously.) As far as not being able to move the feats withing the actor sheet, I'm not sure. That is something to do with Foundry PF2e.
All in all, I hope you can find use for the tool as it is, while understanding it's limitations. I apologize if these limitations make this tool unusable for you otherwise. I created this as a side project, and I will continue to support it as far as it/I can go with it. If you can provide additional details on the points I mentioned above, I will look into trying to get what should be working, working.
