Sometimes the best decision isn't soley based on finances..sometimes people need to spread their wings, and things that are 'easy' to talk about are not easy to do..so your ILS may be finding it not so easy to live with youguys...not that letting thier son go is easier....
On dealing with screaming...umm write it down..try to say it..start with "I would like to finish the whole paragraph..if I can't I will leave it for you to read"..be prepared to leave (leave the house..preferably where she willnot follow), leave the card for her to read...promise to return in a set amount of time..(short if you think she will read it, long if not) ready to discuss...NOT likely to come to a solution of comprimise with parents however!!!! you can try..a good kid would...I wouldn't..but then I lived in my car for a time...not suggesting you do that..just be prepared that she will not listen to a word you say (or your fiancee says)
On rent..get the apartment in your fiances name.....or try school housing...room with someone letting out a room, rather than a whole appartment..rent smaller till you have money to push people around with....(studio apartment..still more yours than a room with the ILS) buy a van and a YMCA membership (for the shower) sleep in the van, shower at the Y..try to work out while you are there
on your parents and signing..you might just have to give something up...I know it seems like you can never have it all, even though it all is soo esy for others to do...but you just might not be able to..people arn't all seeing the same thing you are..your parents certainly are not looking into your best interests right now and nither are your future ILS..you have to pick what is best for you ....and look to your future kids if you plan on having them you will want an amicable relationship with the gmas...and that might be easier to achieve with biting the tounge and leaving...or biting and staying..but regardless so far as I can tell biting the tounge is very neccessary (and mine is constantly bleeding when I am around the MIL!!! not that it doesn't suffer around my mother...)
On information..knowledge is ower..you kept that power form your FMIL, so she is upset about it...maybe you had the right to keep the info..but living with her and the natural need mothers have to know everything makes her a bit testy..tell her you are sorry and move on..not much you can do.. (might even be one of few times her son has held anything from her-bit of a shocker that her kid is growing up? or bit of a scare that her son is leaving her for the other woman...that would be you)
laundry..I am sticking with the laundrymat..again not always the best financial decisiopon, but makes life easier on the homeowner.. Or do it at a friends house if you have any (with house, I am sure you have friends) play poker while the washer runs, take the rest home..play with pennies, lose and consider that paying the electric bill
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Mowign the lawn...if you are home during daylight hours do it..if not..you can't do it afterhours...I am guessing based ont he FIL objection to AM laundry..so you might need to offer a trade...or go buy a push mower...is silent mostly. Or it might be cheaper to pay someone to do it (while the ILS are out so they don't notice) then pay rent on your own..
silly things alot of my post..but I wanted to put out lots of silly ideas...cause humor is the only way I deal with ILS. And as limited as the sane options are..so long as you are willing to step outside there are more options than you might think.