Hi OP
If he is inexperienced then bringing sex toys into the arena has probably scared him so I'd probably put them to one side for the moment and of course you can use your vibrator etc in private.
Re the tummy - I wouldn't worry too much about that. Yes of course it is better when all concerned are in shape and whilst it is a 'negative' it's not one I end a relationship over.
They can definately be 'trained'. I dated someone when I was late thirties and he was early forties and I'm not sure if he had never been in a long term relationship before but it was like he did the very basics to make me come but not a thing extra. Foreplay by numbers sort of thing. I have to admit I didn't bother to teach him anything as we were only together 6 months on and off and he was having a horrible time in his job/had depression.
A few years later we went out a couple of times (he had been in a 2 year relationship) and even though we didn't go the whole way, just a bit of foreplay you could already tell his ex had either taught him stuff or requested stuff and he did seem that he was now more 'experienced' in the art of seduction. Could you try saying 'Oh you know what I love when you do this....' - start small and easy like kiss my neck.
Penis size. Yeah it's a tricky one although I have to say there is such a thing as 'too big' as well. Ex husband looking at you. Seriously though how small is small. One guy I lived with for two years was 'short in length but perfectly fine in girth' and that was okay. The moral of the story being that girth is definately more important than length. Unfortunately another had a very long but very thin penis and honestly I literally couldn't feel anything. That was disappointing and of course not much he could do about it (he was a tall and thin individual so I guess his penis was just in keeping with the rest of him). I sort of got used to it to a degree but yes a bit of a downer for sure. I think you have to look at the whole picture. In my case the guy also thought oral sex for me was below him so i didn't get that either (well once for about 2 mins then never again). So small penis plus nice guy can be acceptable if there is good foreplay, good oral and making the best of it. It's just another 'negative' though to make up the whole picture.
Only you can decide if he can be 'trained' and how small is small.
Bear in mind that some men who have very high sex drives and are good in bed are also cheaters. Looking at you half italian ex. Loved to pleasure his partner. Unfortunately loved all women.
If you like him otherwise and get on outside the bedroom I'd give the training up a go and see if progress is made.
Otherwise you know what to do.........dating is a minefield.