As far as the first gear problem goes, it sounds like it could be a gearbox issue. Worn or bent selector forks or worn synchromesh gears could produce the problems you describe. It might also be a fault with the stick mechanism itself being worn. Does it ever jump out of first when you accelerate? Selector fork problems sometimes result in a particular gear not fully engaging, which means it often pops back into neutral when under load. Also, a very low gearbox oil level might cause such a problem, although this is less likely.

A bad clutch release bearing will make it difficult to engage gears but usually applies to any gear, not a specific one.

The clutch feel sounds like the hydraulic system has either air or water in it. It may not have been bled properly when it was repaired, or the master cylinder reservoir cap might be loose allowing moisture in. Have a look at the hydraulic fluid and check it's transparent and not cloudy, which would indicate contamination. In either case, replacing the fluid and bleeding the clutch hydraulics may well cure that particular problem.

pca