I too live in Brighton and have done for 25years...... tbh we have always moved a little bit further out than our mates to get more for our money (still in city limits). So my advice would be to go west. I think your issue is that you are quite young and brighton is a lively city where people are young at heart. So when I was 20 I wouldnt have dreamed of even living in Preston Park let alone hove as it was "in the middle of no where!". But thats just becuase I wanted to be in the thick of it. Now when I moved to Hove 15 years ago I couldnt have imagined of going to Portslade or Southwick - now it doesnt seem like a bad choice as we go out less, what with work and kids etc.
I know its rubbish but at the end of the day none of us can have it all.
You chose not to work as hard and Brighton wages are notoriously shit. You choose to work in Brighton rather than commute, you chose to have a child and you are now choosing not to go back to night school to requalify to enable you to earn more money in 5-10 years time. In the nicest possible way, these are choices you have made and there are consequences to all of our choices. This is one of the hardest things to accept about being an adult IMO, is that things can be and are your fault / or as a direct result of your actions.
My BF lives in Worthing, and its so much nicer than it used to be when I worked there 15 years ago. 2 bed flat in reasonable and central part (ie near train station) are around £850-900. You can still get to Brighton pretty easily, and you are still by the sea. So I think you need to write down what your top 3 priorities are:
More space / Be by the sea / Dont pay more than £900 in rent - in which case you have to move to Lancing / Worthing / Newhaven - that is just the way it is, and accept you will have to travel to see people.
However if your priorities are: Say in the town we grew up in / Be close to my mum / dont pay more than £900 rent - then you have to stay in a 1 bed flat - and your compromise is having no space.
None of us get all the things we want - I run my own business, and so I aways go to pick my kids up and am with them whenever they need me, never miss sports day etc. And then yesterday when one of y DC was in hospital I was still having to deal with emails. Its called life...... its full of compromises. Sad but true Im afraid. If you lived in a massive house bought 30 years ago in Hove Park, that you now inherited, you would have massive council tax bills, leccie, how would you afford to repair the roof, or get a new kitchen as all of that stuff costs far more money that it needed too. I think you should make a 5 year plan - reskill yourselves, move out to Worthing to not pay more rent and make the best of still living near family and friends.