I found it helped to have two sets of songs to work on:
Songs on the app to practise chord changes and keeping a rhythm
Songs that sounded okay without a backing track, that I could memorise.
For me that second category, for the most part, consists of cheesy country songs with simple rhythms, basic chord sequences, and vocals sufficiently basic that even I could make an attempt to sing along.
I found not having the backing music made it easier to concentrate on the strumming patterns, but having memorised the chords probably helped too.
I’m also in Grade 2, and I struggle with these same issues. This has helped me:
Pick up the guitar, and start playing a song. If I only remember a couple chords, I look at the app (or the tab) and try to commit the rest of just that verse (or other part) to memory. Repeat until I can play all the pieces in sequence. Working this way, it doesn’t take too long to become familiar enough with the song to feel I “know” it. At this point I don’t worry about strumming patterns, or even very much about keeping time - my thought is to make the chords come naturally.
Once I “know” the song, I return to either playing with the app or using the website tab and a metronome, using a simple strumming pattern.
Finally I’ll add in a more interesting pattern.
For me, this keeps things interesting - I’m always progressing, and getting excited about the new bit I’ve learned. It really feels good when my husband tells me I’m getting better! I guess the down side is that my repertoire isn’t very big at this point, but for me that’s ok (I work on songs I really like!).
To put my comments in context, I am just at the end of Grade 1 working on the five songs that I need to play from memory to pass Grade 1.
On your point 1 - After playing along with song on the App for a while, it is a bit time taking but I got the lyrics off the internet and then used the app to put the chords above the words and memorise the sequence to go with the words as I am trying to sing as well. It takes time but it’s working for me. However just recently got Justin’s Tab app for future songs I plan to work on.
Point 2 - I work on strumming patterns away from the app, really I only currently use old faithful with the app. It just takes a lot of practice to get a strumming pattern automatic.
I think I am a bit like you, in being ambitious and trying to incorporate too much at the same time which makes for hard work.
My worst failing is I want to do some of the strumming patterns other than 4D that Justin suggests in the video lesson, makes for a more interesting sound but when there is a chord change half way through bar, it is real challenge.
I see lots of others have made suggestions and they are all good.
For me, the solution was to buy the beginner song books and start to use the webpage and the related videos. It payed off and I started making better progress! Soon enough I stopped to use the app alltogether.
@Socio included a link to my similar question above.
In addition to the answers I got, I have found that picking songs that are not necessarily ones I like listening to, but were relatively simple for me, made them a lot of fun to play - and therefore easier to remember.
Experiment with songs from outside your “favorite listening” list and you may find a few that are more fun to play than listen to!
Bang A Gong and Wish You Were Here are a couple examples for me.
I still struggle with this, but I have a few now that I can remember and am slowly getting some experience with remembering and can start to see a path to doing this more efficiently with more complex songs.