As far as the rules are concerned, Indian citizens require an “airport transit visa” for airside transit in Germany but you are exempted from this requirement by your other visas. Either the UK or USA visa are enough for that, and it's not required to be on your way to the country in question (i.e. holding a valid US visa is enough to exempt you from the airside transit visa requirement when flying to the UK or anywhere else).
The question is therefore whether you will require a regular Schengen visa or not. That depends what you mean by “break the journey”. If you have a ticket to Frankfurt and need to leave the transit lounge to pick up your luggage and check in on the next flight, then you will need it. On the other hand, if you have no luggage or somehow manage to have it checked through or otherwise taken care of, you might be able transit without a visa.
In any case, as @DCTLib explained in his comment, the airline will want to ensure you have the necessary visas before letting you board the flight in India so it's best to check with them. Flying on another airline is not an issue per se but if you have booked the ticket to the UK separately and it looks to Lufthansa as if you would spend a week in Germany, you will likely run into some difficulties.