If I have my dental implant crown removed, will the gum tissue grow back to what it was before the implant healing abutment?

Please upload a photo or more.  I believe unless the photos show otherwise that you are not talking about 75mm  recession.  That is a huge amount.  Let us start over in analysis after we see your photos.  ( There is no tooth in a human being that is longer than 40-50mm ...and I am talking about a giant human!)

Gums tend to regrow around implants when abutments and crowns are removed....to a point and in limited amounts. It really depends. You need to consult a periodontist who specializes in gums and he or she will tell you what should be done long term 

I'm guessing you meant 7.5 mm for the purpose of answering this question. The level of the tissue will change if you remove the crown and recap the implant. That level will be determined by the level of the implant and the bone level. Basically this is hard to guess at without any sort of x-ray or photo. You may require soft tissue grafting to create a more ideal contour. If you are displeased with the result you should discuss your options with your surgeon.