From a tax standpoint, there are additional disclosures to make when selling a business asset for less than fair market value to a related third party. 

Ya have to learn to mitigate multiple hurdles, in addition to making intelligent and educated moves. 

However if you had done a warranty deed (or a special warranty deed if you still have a mortgage on it) instead, your LLC has a claim against you for the issue on the title, and you in turn can go back to your initial title insurance to fix it.Some title insurance will allow to transfer the coverage to an LLC that you own 100%, but not all of them do or they may require an additional fee.

NEVER borrow from a 401K, you are taking pre-taxed dollars and paying it back with after tax dollars, you do not get to return the loan with pre taxed dollars, in addition, some 401K plans do charge interest and maybe even fees, and lastly if you get laid off for some reason, it is a distribution with all the "fun consequences: tax at the last dollar rate, and if you are under 59.5 there is also the additional 10% penalty.Personally I like the HELOC, however you can also sell stocks and do tax harvesting there to offset gains if that is an option

Charging an additional 15% seems a little ridiculous.

They are all pretty the same this one cash flows the least amount but has some additional upside.   

You don’t get to just expense the additional real expenses.

Making additional payments or taking a shorter term are just depositing more into that savings account (it's not like the property appreciates more by paying down the loan). 

These are professionals with additional training and a stricter code of ethics.

@Kleyn LopezI have referrals in the San Diego area if you are in need of additional CPA recommendations.