How can I file an I-485 on a J-1 and as an EB-5 dependent?

That can be visa fraud-your counsel should have advised filing a following to join petition while waiting-poor advice.

You can but there may be an issue of conflicting intent.

After you return to the US, contact me.

Entering the U.S. on a nonimmigrant with the intent to stay and file for adjustment of status could be considered a misrepresentation and could lead to serious problems with your application. I suggest that you reach out to an attorney to conduct a detailed analysis
and develop the best strategy in your case.

You cannot travel to the US on the B-2. This visa does not permit immigrant intent.
Entry on this with an intent to adjust your status via an I-485 would likely give rise to inadmissibility on the basis of fraudulent intent (i.e. claiming to be coming to visit, when you intend to process your GC here.
You must wait to be processed on a following-to-join basis and will need to be processed through the US consulate in your home country.
If USCIS hasn’t already been notified of your husbands adjustment via the I-485, you will likely need to file an I-824 petition seeking to have USCIS notify DOS that he has adjusted his status here, and that you would like notice of this communicated to the Department of State’s National Visa Center. Once USCIS notifies them, which can take between 3 and 12 months, the NVC will then contact you to have your pay the processing fees, and provide details as to what documentation needs to be provided before you can be set up for a green card interview at the US consulate in your home country.
Should you want us to assist you in this regard, kindly reach out through the contact form.

It is inappropriate to travel to the US pursuant to a B-2 visa and thereafter file an I-485. I recommend assessing if you may qualify for either an O-1 visa given that you hold a Ph.D., however, that does require you to find a US employer willing to sponsor you for the O-1. The H-1B could have been another option, but because of the $100,000 additional filing fee, I would imagine it would be challenging to find an employer willing to pay that money.
As an alternative, and certainly something that your husband’s immigration counsel should have advised, he can file Form I-824 to request the USCIS notify the Department of State of your eligibility to immigrate under this “follow-to-join” concept. The process may take 1.5-3 years, but is the most conservative advice an attorney can provide in this situation.