There's a thread devoted to the topic of offshore trading for U.S. residents -- https://forums.babypips.com/t/going-offshore-to-escape-the-cftc/35612?u=clint You should spend some time studying that thread. Answers to all of your questions about trading offshore can be found in that thread.
It's a very long thread, and searching it for answers will be time-consuming. So, I'll give you the short answers to your five questions here. For the long answers, you'll have to tackle that thread.
There are only a few foreign brokers who will accept U.S. residents as clients. We have identified 12 of them. In all 12 cases, accounts can be funded in any one of several different currencies, typically USD, EUR, and GBP. Forex brokers do not do currency conversions. So, if you want your offshore forex account funded in USD, you will have to remit USD to your offshore broker.
The most annoying (and often difficult) aspect of dealing with an offshore broker is money transfer to and from your brokerage account. In almost every case, there are fees of one sort or another which you just have to accept as a cost of doing business. The money transfer options vary from broker to broker. Studying those options is one of the important bits of due diligence you will have to do as part of your selection process.
Your third question has me baffled. If you live in the U.S., then presumably your daily life is denominated in USD. If you want an offshore account denominated in USD, then there is no currency conversion required at any point in the process between your U.S. bank account and your offshore forex account.
Forex profits are taxable income (unless your taxable income from all sources, including forex trading, is so low that you are not required to file a tax return or pay income tax). Taxable income earned in an offshore forex account is taxed just the same as taxable income from a U.S. forex account. However, forex profits (whether earned here or offshore) are a bit tricky. There are two different ways in which those profits can be reported and taxed. You will have to become familiar with the IRS provisions for reporting your profits (and losses), and figuring the applicable taxes. Equally important, in the case of offshore accounts, is the U.S. government requirement to report foreign financial accounts of any kind (regardless of profits or losses earned in those accounts) if the total aggregate funding in all of them combined is equal to or greater than $10,000. This requirement is known as the FBAR reporting requirement, and you must be sure that you are in compliance with it. Failure to do so will get you into more trouble than failing to file a required tax return. Taxes and the FBAR are discussed in the Offshore Broker thread linked to, above.
No, you will not receive anything like an IRS Form 1099 telling you how much profit (or loss) you need to include on your income tax return. Determining those numbers, and being able to prove their accuracy, is your responsibility. And how you do it depends on how you elect to handle your forex trading profits and losses, as described (briefly) in #4, above.
To learn more, join us on the Offshore Broker thread.