I'm a DM who's looking for a good software tool to help me make Battle maps. The way I do things is I make A map here then I save the map and put it on my phone with this then I use it when I DM with a party offline, however It's not a flexible system and it can sometimes crash if I'm not careful. What I'm looking for is a program that allows me to do the following.

-Insert home made tiles and other kinds of props.
-Has the ability to toggle between multiple layers of a dungeon quickly in case I decide to add a balcony or something along that line.
-Be used as both a virtual table top and an editor.
-Allows the use of curved tiles.

Other then that, here's a list of features I'd like but don't necessarily need.

-A hex grid variation.
-A map that can extend to about 5000 squares, crazy yes, but I prefer to use battle maps even if the RPG doesn't intend to work that way.
-Free and online.
-A 3 Dimensional map.

I don't mind if I have to carry around a laptop or something if I can put it on my phone and Price is negligible right now.

Again, if you can find a system that fits these specifications, I would be very grateful. If not, well is there anything else you can recommend for me to use?