How to make academic life bearable under stressing circumstances?
Since you seem to have decided that you must accept the situation where you work, let me make some suggestions to make it less depressive. Some of these might not be good ones for you, so pick and choose those that appeal.


the room. One room for 18 people? They don't seriously expect you to use it. What can you use instead?  Do you meet students there, or write conference papers, or prepare coursework? Can you do those things somewhere more pleasant? Your own living room, a coffee shop, a park bench, a table in the library, a classroom that's empty more often than not? Do you have to sit in a crowded place jammed with broken things, or can you go somewhere nicer and get more done?
no funding for conferences. Good for you managing to get a paper accepted and managing to get yourself there. That's probably one more conference than many of your peers. If there is someone who goes to more conferences than you, go and ask them how they do it. They will probably be happy to show you the tricks. In the same spirit, if you can get your own computer you won't care that the department can't provide decent ones.
intellectual connection. The people in the depressing room are half of your peer set - the other half is the A1 and A2 people around the world. Find them! Follow them on Twitter, read their blogs, download their conference sessions and papers, email them with questions about something they published. Use the internet to forge ties with these people - you aren't a moonstruck teenager, you're their peer and they will be happy to hear from you. Who knows, this activity might even lead you out of your current situation some day, but more importantly it will help you grow and solve a pain point for you.
the rest of your life. It's common to push everything else aside while chasing tenure. Do you have any hobbies or habits? Even just following a sports team? Try to ramp up that side of your existence, make some friends who don't work at the university, spend some time cooking or hiking or reading the latest celebrity gossip or watching that tv show everyone watches. Do some fun stuff, whatever fun is for you. Meet some people who can bring you joy.
find a way to be more connected to the university as a whole, not just your department. Join a club or team that has profs from all faculties, or even better has faculty, staff and students from all faculties. Attend (if appropriate) religious activities that happen on campus. Go to the "our university day at X" events. Help with fundraising or political activities that will let you meet people from all over the campus. You're going to be here a long time right? Get to know the place and the people and weave it into your life.
if the tenure you're expecting comes with a raise, start working out now what the consequences of that are. Will you be able to move to a nicer place? Get specific about looking for that place now. Imagine being able to have a lovely view, or a spare bedroom you can use as an office, or quieter, safer nights. The hard work you have put in will be bringing you benefits soon, start to think about those now.


Your department would be amazing if they handed you a bright sunny office, a delightful collection of peers who you enjoy talking to, plenty of important work, a steady stream of bright students, a fully-equipped working environment and a library that's the envy of everyone in your field. But very few places are really like that. So roll up your sleeves and get yourself what you need to excel, and fill your days with work and not-work that make you happy. Your department is never going to do that for you, but you can do it for yourself.