Yup.
Regarding source code of the admin tools used in competitive matches, I don't think they are open source - there are no other (forum-legal) ways of obtaining the source, but the changes you are looking to make are fairly trivial anyways (assuming The Deluge didn't change too much about the base parts):
- For the timer, you literally just need to find the right number and change it to your liking.
- For the flag spawn location, there is a store_random_in_range somewhere selecting the point out of 3 possibilites - at that point, just introduce a new (global) variable, store the selected location in it and then in the next round, see if the randomized location is the same as in the previous round - if so, reroll/reassign it. [Been a while since I looked at the admin tools but pretty sure it was done like this]
As for actually editing source code, any editor you like will do - some people will recommend gold ol' Notepad++, Visual Studio Code, Sublime Text, etc. - pick what you like/know. Apart from a text editor, you will need python2.x installed - for that (and other modding basics), I suggest you take a look at
this guide.