Tickets for Tower of London
 

Can tickets be purchased at the tube station at Heathrow Airport?

And I'm assuming it's the same line as purchasing tickets for the tube (sorry, I'm slow)

What other tickets can you purchase at the tube?

Yes.
It's the same queue.
Madame Tussaud's, London Eye, London Dungeon, London Zoo, Kensington Palace, Hampton Court Palace and Windsor Castle.

Is there a price break if buying a tube and attraction ticket? And i assume with the pre-bought ticket you skip the lengthy lines to get into the Tower and other sights - you just waltz in sort of, which would seem the best reason to buy the ticket at a tube station???

Are the tickets open ended? Meaning good for any day? I believe this is not true for the London Eye.

thank you

Not sure how much touring you are going to be doing, or how long your trip is, but you might want to check into the Great British Heritage pass and the London 2 for 1 deals http://www.2for1entry.co.uk/ the tower is on 2 for one with 1 adult ticket at half price with the purchase of one at full price.

Great British Heritage passes no longer cover the Tower, Kensington Palace or Windsor Palace as they did last year. Outside of London the GBH pass could be a great deal as hundreds of things are covered but in London it's often not going to save you money.