Tesla_Reloaded

Just a different voice actor for the operator, nothing else.

That's strange. Normally you don't need to log in to receive items you've purchased from official store. So people can get out of negative platinum balance just by buying platinum from the official store and then getting access to their accounts right away. But in your case I'm afraid there's no other way but to wait for a response from the support.
Wouldn't say months, usually between one and three weeks.
Both ways are available - merging and copying. It can be selected manually during the account merge. But I'd suggest you to solve your platinum issue first before going to merge your accounts.
You can find more information about account merging here: https://www.warframe.com/crossprogression
and there: https://www.warframe.com/news/cross-platform-save

That's half-bugged / half-outdated thing from old times when Grineer Forest sabotage mission was just added. It's possible to craft Antitoxin (blueprints still available on the market) and apply it here to gain some (absolutely miserable) rewards by the mission's end. Nobody uses it anymore, of course.
https://warframe.fandom.com/wiki/Antitoxin_(Gear)

Wrong forum section.
https://forums.warframe.com/forum/85-recruitment/

It's called Frontal Artillery or Tunguska Cannon. Its charging time (time when you hold your button to make a shot) cannot be affected. But the number of charges can be changed. If you go to the rear of your Railjack you'll find 4 forges. Each forge can create a new bunch of Tunguska charges. And each time you create a new batch it gives you one extra charge for the duration of your mission chain.
For example, when you start a mission you have only 2 charges. When you craft a new batch of charges it fills out all depleated charges and provides +1 extra charge, giving you 3 charges in total. The next craft will give you 4, then 5 and so on. And that will last through all the railjack misisons you go in a row, until you return to Dojo/Relay Dry Dock.
For more information about the forge visit the wiki page: https://warframe.fandom.com/wiki/Railjack/Gameplay#Resource_Forge
Additionally you can use Artillery Cheap Shot plexus mod that gives 60% chance of not spending a charge when firing Tunguska Cannon.

The trade ban is usually given automatically after the game detects you've gathered abnormal amount of resources during a mission (happens during 2-3 hours long survival runs, for example). Sometimes trade ban can be applied by a mistake, too. But generally there's nothing bad about it (except for being unable to trade) - this trade ban won't lead to overall account ban and won't leave any negative effects on your account. You can safely wait for those two weeks to pass, playing as normal, and the trade ban will be gone on its own.
Since you've already messaged the support you only need to wait. Keep in mind the support is run by humans that can be quite busy answering other tickets. Be patient, you support ticket will be answered eventually.