What you should tell your lawyer is more or less: "I am planning to file for divorce in a year or so. My wife and I have a lot of equity in the house. What should I do now to maximize the probability that I will get my fair share of the equity during divorce".
You will generally be better off selling the house before you divorce. It will be easier to split the money than to split the house. Talk your wife into selling the house and moving, then file for divorce before
buying another house. Or see if you can talk her into selling the house because “the market is overvalued” or for any other reason.
Another thing you can do is take the second mortgage with a private source and withdraw equity from the house. It may backfire against you during divorce, but people do withdraw all equity from their house and “gamble” it away, etc.
Do not do home improvements or buy new furniture.
Everything you spent on improvements and furniture will likely benefit your wife only after you divorce. You will spend thousands and thousands of dollars on improvements, your wife will keep all of it, and you will be stuck with the debt.
Keep the assets you had prior to marriage (or property received during marriage by gift or inheritance) separate from the assets you acquired during marriage.
Hopefully you have already been doing that all along. Now is certainly not the time to mix any assets you owned before marriage (or property received during marriage by gift or inheritance) and assets you acquired during marriage.
Get a credit report that lists all your accounts and credit cards.
You need to know exactly what you have before you can decide which accounts and credit cards to close.
Gradually cancel your credit cards.
But make sure and leave the card(s) your wife is using opened for now. Cancel the cards your wife is using right before you announce divorce. Start paying cash for things. The less credit cards you have opened, the less credit card debt she can run up before (or after, you may still be liable for that as well) the divorce. Also, the less records of your pre-divorced life there are, the better. Her divorce lawyer will have less material to work with.
Keep as much of your assets under your name only as possible.
Transfer as many assets under your name only as you can get away with.
Cash checks that are not your regular paychecks instead of depositing them.
The less records of your income and deposits, the better.
Consider filing bankruptcy before, during, or after divorce.
Bankruptcy will not discharge alimony and child support, but it will generally allow you to get rid of