I agree with Terez. For the time being focus on pieces that within your capabilities. Once in awhile add a piece just a notch or two higher in difficulty to stretch your abilities--but not Rachmaninoff. Not yet. Rome wasn't built in a day.
Slow practice is essential as Terez states. The best way to avoid wrong notes and correcting them is to not play any notes until you are certain from the score and the positioning of your fingers that you have the correct notes in hand. Only then play them. The tactile aspect of playing piano can quickly form habits, and bad ones at that, such as wrong notes. The approach, therefore, is to be alert, cautious, and careful when learning the notes. Doing 10 or 20 corrective repetitions, as you mention, might actually be too many. The more the repetitions, the more opportunity for another wrong note to occur--meaning two or more habits to undo. The optimal number of repetitions varies by person. If you can be watchful, and leave a bit of time between each repetition rather than doing repetitions headlong in rapid order, the more likely that each repetition will be played successfully and the correction will take hold. If you can get down to about six repetitions or so, you'll reduce the chances of compound errors.
Practice demands deep and sustained concentration. That is what enables one to solve problems and to effectively achieve musicality (and avoid wrong notes). When you're practicing, spurious thought entering your mind, or allowing your attention to wander, will invite errors--meaning more corrective action. So once concentration seems to be breaking, it's time to quit practicing and to go on to something else.
I agree with Terez's thoughts on relaxation too. You should be seated such that you're positioned only on the front half of the bench. Thighs should be parallel to the floor. Elbows should be level with the keyboard and should be floating freely such that they can move easily away from the body as needed. Wrists should be extended naturally and neutrally from the forearms, and they must be totally flexible in terms of vertical and lateral movement. Hands should have some arch to them (although there come times when we play best with flat rather than curved fingers).
The playing mechanism as described above needs to be relaxed. The only part of the mechanism that cannot be relaxed are the fingers themselves. They need to be sufficiently taut, otherwise they'll be cottony and unable to play the piano. Be aware of your state of relaxation or tenseness. In particular be aware of your shoulders. As you practice, there can be a tendency for them to creep upward to the point where you feel neck pain. Whenever that occurs, remind yourself to lower your shoulders (forming a beneficial habit). If your arms become tense, stand up swing them and dangle them like ropes in a wind to remove the tenseness. It only takes seconds.
On reading music: Before you start a piece at the piano, take the score and a pencil and first sit in your living room to analyze it. What is the character of the piece? A march? Lovely nocturne? A waltz? A quiet reverie? Colorful Spanish music? This will guide your general approach to the music. Notice the key signature and look at the time signature. As you read the score, if there are ledger line notes that you cannot read instantly, figure them out and pencil them in. Take careful note of the tempo and/or mood markings (if you don't have a musical terms dictionary, get one) and notice where the dynamics change throughout the piece. Does the piece contain some tricky rhythms, perhaps a section with polyrhythms between the hands? This is the time to figure them out, perhaps with the help of the metronome as you tap them out. If fingerings are given, they might be good or not so good. Everyone's hands are different. Plus, the fingering might have been devised by a genius like Joseffy, or by a person being paid by the page or hour. Consider all fingerings tentative include ones that you devise yourself. You can always make more suitable adjustments. Look at the composer's figuration. Is it mostly chordal? Rapid scalar passages? Long legato cantabile phrases? Broken chords? The passage work the piece contains will dictate the techniques you bring to bear in the execution. Once you've done this analysis, when you sit at the piano, some elements of the piece will be more readily understood and more easily accomplished. So think of practicing both away from the piano and at the piano.
If it might be possible for you to find an excellent teacher and to continue lessons after the long hiatus, you would benefit tremendously. And many teachers love to have adult students. Something to consider.
I hope this helps.
"Interpreting music means exploring the promise of the potential of possibilities." David April