Assuming this is a New Jersey matter, unless the attorney's prior representation of the complainant involved anything dealing with the criminal charge, (doubtful since it was a real estate transaction or transactions) there would not be a conflict of interest. Previously New Jersey had the "appearance of impropriety" rule. That was removed by the Supreme Court in recent years. So, even if it appears to be wrong, unless there is a direct conflict, there is no wrongdoing.
As to the...
It is 6 years from the date you discovered the malpractice. If you don't know your attorney committed malpractice and then you discover that he/she did and it is 5 years ago, you stillhave another 6 years to sue. But if you had good reason to know, and you just didn't bother to really find out, this could be held against you.
If the Landlord is responsible for supplying heat and he failed in this responsibility, if you give him a written notice (not telephone) by Certified Mail, that you intend to deduct the cost of the repair from your rent payments. Then, if he tries to evict you you may raise this as a defense. In New Jersey this is called a Marini vs. Ireland defense.
I would guess that the HELOC, a second mortgage was eliminated from a claim in the foreclosure by the first mortgage. They probably sold their rights under the Note you signed to United Guarantee at a large discount, since they lost their rights to the property. Your attorney should inquire as to what United paid for the assignment of rights. This may, in some jurisdictions, limit their right of recovery.