I don’t have a problem with the lithuanian IBAN. Sometimes a little IBAN discrimination here and there, but always cleared this up by explaining the legal offence of IBAN discrimination. I think a german IBAN will cause much more surveillance by the governments (Bafin, …, …). Hope I can choose to keep the lithuanian IBAN.
Of course federal agencies have access to your Revolut account. It even can get seized. Do not forget, that you gave your tax-number to Revolut with your registration
Yes, but it might be a little more difficult for federal agencies to get access to a Revolut account. Most of german offices and authorities do not even know what Revolut is. The german Jobcenter recently sent the inspection service to me, because they thought I have my centre of life in Lithuania. 
I explained them already in detail before, what a Revolut account is and I thought anything is done with that.