The only way this is possible would be to use a plugin. Plugins can modify what is and isn't allowed on servers, so, for example, you could have someone freeze in their spot if they equip a gun on round one.
However, most likely nobody made a plugin for what you want yet, but if you make an account on these forums, and request a plugin, hopefully somebody can make a plugin suiting your needs.
I'll get questions 2 and 3 out of the way first. In the CS:GO authoring tools, open the Workshop Map Publisher. This is where you input all your information about your map, including name, a short description, and what game mode. As soon as you click publish, your map will be on the workshop, give or take some Valve Time.
Before you do any hosting, you'll need to forward ports in your router. Find your router in this list, and you will be guided on how to forward the ports needed for CS:GO.
I would highly recommend starting listen server, a server hosted while you're playing CS:GO and will be shutdown when you disconnect, rather than a dedicated server. Dedicated servers are used only if you're going to be hosting for a very long time.
First, place your completed map in %steamapps%\common\CS:GO\csgo\maps\
Then, go to this website, and jot down your IP address. You'll give this out to your friends.
Now, start CS:GO, and open the console with the tilde key, `, then type map your_map_name and hit Enter. Once your map loads, open the console again, and input sv_lan 0, this will allow other players to join.
That's it! Other players will be able to join with the console command connect your.ip.here. Just make sure they've downloaded your map from the workshop before they connect.
NB: If players cannot connect to your server, open the Steam Overlay, head over to CanYouSeeMe.org, and enter port 27015. If this test fails, players will not be able to connect; make sure all your ports are forwarded correctly.
Best Answer
If you're looking for a deathmatch server with pistols only, you could try this plugin (requires SourceMod and MetaMod).
Else, you could try using this plugin to restrict weapons (also requires SourceMod and MetaMod).