I think the advice you have been given by
@alex-z is reasonable.
In large part because it quite accurate.
Nobody is dissuading you from DIY. Go for it and start learning. You are at the beginning and obviously have a lot to enjoy learning. Be cool being on your own, taking something apart that you may not be able to put back together - though you will learn and hopefully have some frustratingly fun times.
Beyond that it seems you feel entitle to avoid constructive criticism and have others hold your hand on what is likely a very uninteresting project for more experienced builders. This speaker is not a diamond in the rough that just need a little TLC. It is not a good speaker to mod for anyone with valuable time. Best not to kid yourself that your project offers something for very many others. You'd like folks to spend valuable hobby time and yet you don't want to spend $80 on an accurate microphone so it all seems a bit off. Which is fine - that is part of the learning curve, realizing this is a big investment of time and sometimes more money then seems to make sense unless you really want to be in the game.
The rockwool batting will not really help this speaker nor will any sort of $25 crossover.
All the people with experience know this just with a glance at the data and speaker and so will be unlikely to want to help you go down a valuable learners dead end. This is a 2+2=4 calculation.
Likely all of us have done this sort of thing back in the beginning, so I do understand why you maybe want to give it a go no matter what. You start where you start.
1. It needs oak Dowling or ply/MDF bracing in the cabinet, some 3 layer SonicBarrier on the cab walls
Sonic Barrier 3/4" 3-Layer Acoustic Sound Damping Material with PSA 18" x 24"The Sonic Barrier 3/4" 3-layer composite damping material is a premium acoustic absorption and barrier material. It uses the three layers to achieve excellent reduction of sound energy from the inside of the enclosure...
www.parts-express.com
2. It need a complete crossover rework.
For a competent 3-way using low quality drivers (and thus more elements required to flatten and shape the poor driver responses) expect to spend $65-100 per speaker. Plus extra parts to switch things around a bit for the final tuning.
3. The drivers are high distortion and perhaps need to be re envisioned.
4. The dispersion is way off from "good" in terms of what most folks like. This can not be effectively changed unless drivers are changed and cabinets modified.
As was mentioned if you really want to tinker here, buy a PEQ and play around with DSPing the sound. It will be interesting say I. Plus that way the investment can be used on a better speaker in the next go around.
There are dedicated DIY audio sites that have a wide range of DIY interests and levels and maybe folks who might be more able and willing to help. If I was you I'd be hard pressed to anticipate DIYers who are on a site that uses a $100,000+ measurement system to be much into designing this speaker by ear or by Iphone mic (which while better than nothing is not nearly as accurate as a proper mic, it can work for bass corrections). Especially at the extreme beginner level of your approach.
IMhumbleHO any offense you are taking and your aggressive accusations are misguided.