Your question isn't silly. Your gut is saying 'something is not right about this' but you can't be sure given the emotional and wrought reality of splitting up, that you're not just being 'vengeful' because emotions are at an all time high. Your instinct is that you don't want to make things any worse for yourself.
Your STBXH may be right - it is not worth spending a lot of money on solicitors if there's not much to fight over to begin with. Getting a solicitor involved has to make financial sense. The divorce process does not concern itself with who did what to who - that's the stuff of movies.
Getting a solicitor involved is not an act of revenge, it has to be because the financial package is very unfair to you and clearly advantageous to him. If it is about ego - then don't hire one beyond the initial meeting.
A word of warning: by not doing as he says, and doing things for yourself, you are possibly going to get a lot more bullied over time - another reason for having a solicitor, they take the pressure off quite a bit. But this will ramp up your costs. But be prepared for you STBXH to become a dick of the highest order if you defy his argument to not get a solicitor involved, and your solicitor doesn't agree his offer is 'reasonably fair'.
However, only employ a solicitor if the cost of doing so will definitely result in you being between 5K and 20K better off at the end of it. A solicitor cannot take away the pain of your divorce, but they can explain your rights and suggest what a possible reasonable settlement would look like.
There are people out there who wish to take their spouses to the cleaners - it's not going to happen. We aren't in an 'Hollywood happy ever after scorned wife gets revenge movie'. This is real life.
You don't mention children or the length of your marriage, or your ages. This is a very important consideration when getting a settlement. A 55yo SAHM will get infinitely more in a settlement than a 25yo SAHM, when the needs have been met for both parties.
I only went to see my solicitor to get advice on the process and what I had to do. She's been my rock for the last three months, and likely to be for the next year - and she has already secured a better interim financial package for me than he 'generously' offered, so has paid for herself many times over already. So glad I didn't know much about divorce really, and my instinct was right.