Keep in mind what I'm listing below are options. Maybe someone else will have even better ideas to suggest that may keep things even closer to what you want.
1 - Action bar mods are out there and
Dominos or
Bartender4 are good places to start. They are easily customize-able and do the things you mentioned.
2 - Outside of a mod like
UnitFramesPlus which I'm not sure if it still works you may have to look at a complete unit frames mod. Things like
StufUnitFrames or
PerlClassicUnitFrames are two out of many.
3 - You can turn on the floating combat text in blizzards own interface options. However if you mean you want it fully customized then you would need to look into mods like
MikScrollingBattleText or
XCT+.