Usual causes:

1. Air flow set too low.

2. Filter clogged.

3. Refrigerant low.

Of course, there can be other causes but these three are the ones to check first. If you have already checked them, check them again and confirm you earlier findings.

I think you may need to get a second opinion from someone other than your mom's boyfriend.

The above video should come with a warning to potential viewers that they might just be dumber after viewing it then they were prior to viewing it.

Disclaimer: I have no formal training in HVAC repair. My comments are based on personal experiences with HVAC equipment.

We changed out the blower motor, and it is fully charged up on refrigerant. It also does not blow very cold like it used to,

Was the AC able to keep the house cool on a hot summer day after the repairs were made?

It also does not blow very cold like it used to, it definitely could be stronger cold air coming out.

If the air is not as cold as it was in the past, then it is possible there is a refrigerant leak. Adding refrigerant without fixing the leak is a temporary, expensive, and bad practice. The low refrigerant charge can also cause the coil to freeze. If the air flow seems weaker than previously then the new blower motor could be undersized or not set to the proper speed setting.

My mom's boyfriend has an hvac company he runs and we are just seeking advice from others on what it could be as far as the issue.

The owner of an HVAC company should have the skills to fix the problems you are describing in my opinion. If not then he needs additional training or consider another line of work. My advice is to hire a competent HVAC repair company and do it before the summer heat begins.

We know the duct work the people who remodeled the house had put in is not big enough for the unit we have, so finding that out, pretty sure that is the issue. It's not getting enough airflow for the unit that we are running. The duct work can only handle 960cfm, where my unit needs 1600cfm.

The duct work can only handle 960cfm, where my unit needs 1600cfm.

How long have you owned this house?

This suggests the unit may be oversized. How big is the house? How many sq. ft? Ceiling height? windows / where they are positioned? Size of such?

How old is the house? (to give an idea of how well or not so well the thermal envelope may be or not)

Many things go into getting an AC to work properly. While sizing is important, it's not the only thing to consider. People, money and the choices they make because of the lack thereof.

No one (in their right mind) is going to put a 4 ton system on ductwork that is suitable for a 2.5 ton system.

Sounds like you're in a really bad spot if you ask me. (it's a guess off what you've said that I printed above)

I service the Katy, Texas area.

We know the duct work the people who remodeled the house had put in is not big enough for the unit we have, so finding that out, pretty sure that is the issue.

You are providing important information but diagnosing the problem remotely is not going to work. Was the original duct work properly sized, and then made smaller during the remodeling?