Pipes- sounds like the pipes are at best corroded/clogged with scale in some areas. That would explain hot water qickly in some places, not so much in others. This isn't uncommon, especially in older houses.

Chimney/fireplaces- the gas logs can be taken out, and the fireplaces can be used as wood fireplaces BUT the chimneys should be inspected and cleaned prior to use. We had 3 fireplaces/chimneys cleaned and inspected for about $250.

Windows- depends on how handy you feel. If you can use a level, a square, screw gun and caulking gun they aren't that hard to replace. From the dimensions you list I'm assuming you have multiple sashes in some windows, in which case you would measure each sash and replace each one in turn. depending on the size and what you use for replacements, they run $100 for a small window to $250 for a larger window. (those prices are for the windows themselves, not installation) Most home centers will have classes on how to both measure and install replacements.