In order for your car loan & installment loan to your credit report AND impact your credit scores, the *creditor* will need to choose to report them to the credit bureaus. Creditors are *not* required to report items to your credit report, however if they do, what they report must be factual.
A loan officer can assist with modifying *existing* trade lines that are already on your credit report, and modifying them could increase your credit scores, but they cannot add trade lines that are not on there and have your score change because of it. They can document that you've been paying those items through what is called a "credit supplement", but that does not impact your scores, that is just an addendum from the credit vendor the loan officer uses as a 3rd party verification that you had the car loan & installment loan on time.
I've been reading your questions for a few weeks now and I feel you will get a lot of help if you just have a 1-on-1 talk with a loan officer who'd be willing to candidly answer every and all questions you ever have about qualifying for a mortgage - from why the scores they pull aren't the same as the ones you get from websites, to what you can do to improve your credit & credit scores, to what potential loan programs you'd have to qualify with once your credit is in the condition it needs to be to qualify.