When I first started sailing my boat, I had mainsail issues, too. But I just sailed and had fun. Over time, I made incremental improvements on how I set and trimmed the sail. Yes, my sail is old and yes, I might see lots of improvement when I replace it. However...I'm glad I used the opportunity to learn how to properly rig the sail I have.
If your sail can't be raised higher than you show in your photos, you'd be wise to figure out why and fix that before you buy a new sail. My boat had that problem and it went away when I cleaned and dry-lubed the sail slugs. I also lifted the boom by hand so that is wasn't jamming in the mast slot or causing the lower slugs to be jammed. Now, I keep the boom set higher than it should be for sailing, and release it after I get the head fully raised to the top of the mast. Then I set the downhaul. Your boat may work differently; part of the fun is figuring it all out. After you've done that is the time to buy a new sail, IMO, but you may find that you don't need one to suit your purposes for several more years.